Sunroof (pronounced suhn-roof)
(1) A section of
an automobile roof (sometimes translucent and historically called a moonroof)
which can be slid or lifted open.
(2) In
obstetrics, a slang term used by surgeons to describe the Caesarean section.
1952: A compound
word, the construct being sun + roof. Sun was from the
Middle English sonne & sunne, from the Old English sunne, from the Proto-West
Germanic sunnā, from the Proto-Germanic sunnǭ, from the primitive Indo-European
shwen-, oblique of sóhw (sun).
The other forms from the Germanic included the Saterland Frisian Sunne, the West Frisian
sinne, the German Low German Sünn, the Dutch zon, the German Sonne and the Icelandic
sunna. The forms which emerged without
Germanic influence included the Welsh huan, the Sanskrit स्वर् (svar) and the Avestan xᵛə̄ṇg. The
related forms were sol, Sol, Surya and Helios. Roof was from
the Middle English rof, from the Old
English hrōf (roof, ceiling; top,
summit; heaven, sky), from the Proto-Germanic hrōfą (roof). Throughout the
English-speaking world, roofs is now the standard plural form of roof. Rooves does have some history but has long been
thought archaic and the idea there would be something to be gained from
maintaining rooves as the plural to avoid confusion with roof’s the possessive never
received much support. Despite all that,
rooves does seem to appear more than might be expected, presumably because there’s
much more tolerance extended to the irregular plural hooves but the lexicographers
are unimpressed and insist the model to follow is poof (an onomatopoeia describing
a very small explosion, accompanied usually by a puff of smoke), more than one
poof correctly being “poofs”. In use, a poof was understood as a small event but that's obviously a spectrum and some poofs would have been larger than others so it would have been a matter of judgement when something ceased to be a “big poof” and was classed an explosion proper. Sunroof is a noun (sometimes hyphenated); the noun plural is sunroofs.

1973 Lincoln Continental Mark IV with moonroof.
Sunroofs existed
long before 1952 but that was the year the word was first adopted by
manufacturers in Detroit. The early
sunroofs were folding fabric but metal units, increasingly electrically
operated, were more prevalent by the early 1970s. Ford, in 1973, introduced the word moonroof (which
was used also as moon roof & moon-roof) to describe the sliding pane of one-way glass mounted in the roof panel over the passenger compartment of the
Lincoln Continental Mark IV (1972-1976).
Moonroof soon came to describe any translucent roof panel, fixed or
sliding though the term faded from use and all such things tend now to be
called a sunroof.
Lindsay Lohan standing through a sunroof: Promotional photo-shoot for Herbie Fully Loaded (2005).
Manufacturers in the
1970s devoted sizeable resources to develop the sunroof because at the
time, the industry’s assumption was the implications of US FMVSS (Federal Motor
Vehicle Safety Standards) 208 (roll-over protection, published 1970) fully
would be realized, outlawing both convertibles and hardtops (certainly the
four-doors) but the election
of Ronald Reagan (1911–2004; US president 1981-1989) in 1980 changed the
regulatory climate. Reagan, not fond of
dopey rules which impinged freedom, assured Detroit there’d be no ban and the
first American convertibles since 1976 soon appeared, one consequence of which
was legal action brought by some who had purchased (and stored with
expectations of profit) 1976 Cadillac Eldorados, claiming they had been induced
to buy because of the promotional campaign by General Motors (GM) using the
phrase "the last American convertible”.
The cases were dismissed on the basis that GM's statements were “reasonable
at the time, based on advice from government”.
No action was possible against the government on several grounds,
including the doctrines of remoteness and unforeseeability.

Following Lindsay Lohan's example: President Xi standing through a sunroof, on parade in Hongqi L5 state limousine, Beijing, 2019.
The highlight of
the ceremonies marking the 70th anniversary of the founding of the People's
Republic of China (PRC) was the military parade, held in Beijing on 1 October
2019. Claimed to be the largest military
parade and mass pageant in China's 4,000-odd year history (and the last mass gathering in China prior to the outbreak in Wuhan of became the COVID-19 pandemic), the formations were reviewed by the
ruling Chinese Communist Party’s (CCP) General Secretary Xi Jinping (b 1953;
paramount leader of the PRC since 2012).
The assembled crowd
was said without exception to be “enthusiastic and happy” and the general secretary's conspicuously well-cut Mao suit was a nice nostalgic touch.

Two generals of the Belarus army take the salute standing in Honggi L5 Parade Convertibles, Minsk, Belarus, June 2017.
Independence Day in Belarus is celebrated annually on 3 June and there is always a significant military component. Other than the PRC, Belarus is the only known operator of the Honqqi and the four-door convertible parade cars were apparently a "gift" (as opposed to foreign aid) from the Chinese government but the aspect of this photograph which attracted some comment was whether the
hats worn by generals in Belarus were bigger
than the famously imposing headwear of the army of the DPRK (Democratic People’s Republic of Korea (North
Korea)); analysts of military millinery appeared to conclude the dimensions were similar. Purists traditionally describe this style of coach-work as "four-door cabriolet" and it was "
Cabriolet D" in the Daimler-Benz system but the "parade convertible" is a distinct breed and often includes features such as grab bars for those standing, microphones and loud-speakers so the “
enthusiastic and happy” crowd don't miss a word.

Hongqi L5 state limousine.
The car carrying President Xi was the Hongqi L5, the state limousine of
the PRC, the coachwork styling a deliberately retro
homage to the Hongqi CA770,
the last in the line (dating from 1958) of large cars built almost exclusively
for use by the upper echelons of the CCP.
Most of the earlier cars were built on the large platforms US
manufacturers used in the 1960s and were powered by a variety of US-sourced V8
engines but the L5 was wholly an indigenous product, built with
both a 6.0 litre (365 cubic inch) V12 and 4.0 litre (245 cubic inch) V8
although neither configuration is intended for high-performance.
Interestingly, although Hongqi L5 have produced
a version of the L5 with four-door convertible coachwork as a formal parade car
and they have been used both in the PRC and in Belarus, the general secretary
conducted his review in a closed vehicle with a sunroof.

US President Richard
Nixon (1913-1994, US president 1969-1974) with Anwar Sadat (1918–1981;
President of Egypt 1970-1981) in a 1967 Cadillac convertible, Alexandria,
Egypt, June 1974. On that day, the motorcade was 180-strong and unlike the reception his appearance in the US now induced, the Egyptian crowd really did seem genuinely enthusiastic and happy. Within two months, in disgrace because of his part in the Watergate Affair, Nixon would resign.
The CCP
didn’t comment on the choice of a car with a sunroof and it may have been made on technical grounds,
the provision of a microphone array presumably easier with the roof
available as a mounting point and given the motorcade travelled a higher speed
than a traditional parade, it would also have provided a more stable platform for
the general secretary. It’s not thought
there was any concern about security, Xi Jinping (for a variety of reasons) safer
in his capital than many leaders although heads of state and government became
notably more reticent about travelling in open-topped vehicles after John
Kennedy (1917–1963; US president 1961-1963) was assassinated in 1963. Some, perhaps encouraged by Richard Nixon being
greeted by cheering crowds in 1974 when driven through the streets of Alexandria (a
potent reminder of how things have changed) in a Cadillac convertible, persisted
but after the attempt on the life of John Paul II (1920–2005; pope 1978-2005) in
1981, there’s been a trend to roofs all the way, sometimes molded in
translucent materials of increasing chemical complexity to afford some protection from assassins.
Military parade marking the 70th anniversary of the founding of the PRC, Beijing, China, 1 October 2019. Great set-piece military parades like those conducted by the PRC and DPRK (recalling the spectacles staged by both Nazi Germany (1933-1945) and the Soviet Union (1922-1991) are now packaged for television and distribution on streaming platforms and it may be Donald Trump (b 1946; US president 2017-2021 and since 2025) was hoping the "Grand Military Parade" he scheduled in 2025 for his 79th birthday (ostensibly to celebrate 250 years since the formation of the US Army) would display the same impressive precision in chorography.

Covering all possibilities during the 24 hour cycle. US advertisement (1974) for the Renault 17 Gordini Coupe Convertible, the Gordini tag adopted as a "re-brand" of the top-of-the-range R17 (1971-1979). Gordini was a French sports car producer and tuning house, absorbed by Renault in 1968, the name from time-to-time used for high-performance variants of various Renault models.
Renault over the decades made the occasional foray into the tempting US market but all ended badly in one way or another, their products, whatever their sometimes real virtues, tending not to be suited to US driving habits and conditions. Sunroofs had long been popular in Europe and, noting (1) what was assumed to be the demise of the convertible and (2) Lincoln's coining of "moon roof", Renault decided Americans deserved a sunroof, moonroof & starroof, all in one. Actually, they got even more because there was also a removable, fibreglass hardtop for the winter months, Renault correctly concluding there would be little demand for a rainroof. Physically large as it had to be, unlike a targa top, the 17's panel was intended (like other hardtops) to be stored in a garage until the warmer months. One quirk of the R17's nomenclature was in Italy, in deference to the national heptadecaphobia, the car was sold as the R177 but the Italians showed little more interest than the Americans.
Porsche, sunroofs, weight distribution and centres of gravity
Porsche 917K, Le Mans, 1970.
Porsche in the early 1970s enjoyed great success in sports car racing with their extraordinary 917 but greatly innovation and speed disturb the clipboard-carriers at the Fédération Internationale de l'Automobile (the FIA; the International Automobile Federation) which is international sport's dopiest regulatory body. Inclined instinctively to ban anything interesting, the FIA outlawed the 917 in sports car racing so Porsche turned its glance to the Can-Am (Canadian-American Challenge Cup) for unlimited displacement (Group 7) sports cars, then dominated by the McLarens powered by big-displacement Chevrolet V8s. Unable to enlarge the 917's Flat-12 to match the power of the V8s and finding their prototype Flat-16 too bulky, Porsche resorted to forced aspiration and created what came to be known as the "TurboPanzer", a 917 which in qualifying trim took to the tracks with some 1,500 horsepower (HP). There's since been nothing quite like it and for two years it dominated the Can-Am until the first oil shock in 1973 put an end to the fun. However, the lessons learned about turbocharging the factory would soon put to good use.

The widow-maker: 1975 Porsche 930 with the rare and surprisingly desirable (for some) “sunroof delete” option.
Introduced in 1975, the 911 Turbo (930 the internal designation) had been intended purely as a homologation exercise (al la the earlier 911 RS Carrera) so the engine could be used in competition but so popular did it prove it was added to the list as a regular production model and one has been a permanent part of the catalogue almost continuously since. The additional power and its sometimes sudden arrival meant the early versions were famously twitchy at the limit (and such was the power those limits were easily reached if not long explored), gaining the machine the nickname “widow-maker”. There was plenty of advice available for drivers, the most useful probably the instruction not to use the same technique when cornering as one might in a front-engined car and a caution that even if one had had a Volkswagen Beetle while a student, that experience might not be enough to prepare one for a Porsche Turbo. When stresses are extreme, the physics mean the location of small amounts of weight become subject to a multiplier-effect and the advice was those wishing to explore a 930's limits of adhesion should get one with the rare “sunroof delete” option, the lack of the additional weight up there slightly lowering the centre of gravity. However, even that precaution may only have delayed the delaying the inevitable and possibly made the consequences worse, one travelling a little faster before the tail-heavy beast misbehaved.

Porsche 911 Carrera S, Pacific Coast Highway in Santa Monica, Los Angeles, June 2012.
Although it seems improbable, when in 2012 Lindsay Lohan crashed a sunroof-equipped Porsche 911 Carrera, it's not impossible the unfortunate event may have been related to the slight change in the car's centre of gravity when fitted with a sunroof. She anyway had some bad luck when driving black German cars but clearly Ms Lohan should avoid Porsches with sunroofs.
The interaction of the weight of a 911’s roof (and thus the centre of gravity) and the rearward bias of the weight distribution was not a thing of urban myth or computer simulations. In the February 1972 edition of the US magazine Car and Driver (C&D), a comparison test was run of the three flavours of the revised 911 (911T, 911E & 911S), using one of each of the available bodies: coupé, targa & sunroof coupé, the latter two with additional weight in the roof. What the testers noted in the targa & sunroof-equipped 911s was a greater tendency to twitchiness in corners, something no doubt exacerbated in the latter because the sliding panel’s electric motor was installed in the engine bay. C&D’s conclusion was: “If handling is your goal, it's best to stick with the plain coupe.”
The Porsche 911 E series and the Ölklappe affair
1971 Porsche 911S (note the flap for the oil filler cap behind the passenger-side door (US market model and thus left-hand drive (LHD)). The factory confirmed this car was built in July 1971, despite many references to E series production beginning in August.
Although in C&D's 1972 comparison test there was much focus on the rearward weight bias, the three 911s supplied actually had a slightly less tail-heavy weight distribution than either that season's predecessor or successor. Porsche in 1971 began the build of its E series update (produced between July 1971-July 1972 and generally known as the “1972 models”) of the then almost decade-old 911 and in addition to the increase in the flat-six’s displacement from 2.2 litres (134 cubic inch) to 2.3 (143) (although always referred to as the “2.4”), there were a myriad of changes, some in response to US safety & emissions legislation while others were part of normal product development. One of latter was the placing of the hinged-flap over the oil filler cap behind the right side door, something necessitated by the dry sump oil tank having been re-located from behind the right rear wheel to in front, one of a number of design changes undertaken to shift the weight distribution forward and improve the handling of the rear-engined machine’s inherently tail-heavy configuration. In Germany, the addition was known variously as Ölklappe, Oil Klapper or Vierte Tür (fourth door, the fuel filler flap being the third). Weight reduction (then becoming difficult in the increasingly strict regulatory environment), especially at the rear, was also a design imperative and the early-build E series cars were fitted with an aluminum engine lid and license-plate panel although these components were soon switched to steel because of production difficulties and durability concerns.

Where the troubles began: The fuel filler flap on the left-front fender (left) and the oil filler flap on the right-rear fender (right). Apparently, not even the “◀ Oil” sticker in red was sufficient warning.
For the E series 911s, Porsche recommended the use of a multigrade mineral oil (SAE 20W-50 or SAE 15W-40, depending on climate) but were aware those using their vehicles in competition sometimes used a high-viscosity SAE 50 monograde. With the car’s 10 litre (10.6 US quarts, 8.8 Imperial quarts) oil tank, the fluid’s weight would be between 8.5-9.1 kg (18.7-20.0 lb) and the physics of motion meant that the more rearward the placement of that mass, the greater the effect on the 911’s handling characteristics. It was thus a useful contribution to what would prove a decades-long quest to tame the behaviour of what, in the early versions, was a car regarded (not wholly unfairly) as handling like “a very fast Volkswagen Beetle” and ultimately the engineers succeeded, it being only at the speeds which should be restricted to race tracks the 911s of the 2020s sometimes reveal the implications of being rear-engined.

VDO instruments in 1971 Porsche 911S. In home market cars, the oil pressure gauge (to the left of the centrally mounted tachometer) was labelled DRUCK.
However, when in August 1972 the revised F series entered production, the oil tank was back behind the rear wheel and the filler under the engine lid, the retrogressive move taken because there had been instances of gas (petrol) station attendants (they really used to exist) assuming the oil filler flap was the access point for the gas cap and, to be fair, it was in a location used for gas on many front-engined cars (a majority of the passenger-car fleet in most markets where Porsche had a presence). Quite how often this happened isn’t known but it must have been frequent enough for the story to become part of the 911 legend and the consequences could have been severe and rectification expensive. The factory paid much attention to oil and also ensured drivers could monitor the status of the critical fluid; all air-cooled 911s ran hot and the more highly tuned the model (in 1971-1972 the 911T, E & S in increasing potency), the hotter they got. As well as being a lubricant, engine oil functions also as a coolant and the VDO instrumentation included gauges for oil level, oil temperature, and oil pressure; for all three to appear in a road car was unusual but being air-cooled and thus with no conventional fluid coolant, the oil's dynamics were most important.