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#4384736 - 04/20/17 11:30 PM Older cars = shorter oil change intervals, why?
antik Offline


Registered: 03/29/15
Posts: 23
Loc: Australia
Just wondering why cars from say mid to late 90's have way shorter oil change intervals compared to today's cars? Cars from the 90's are normally every 5k-7k kms where as today 15k-20k kms isn't unnormal. Is it just due to the higher quality synthetic oils available today compared to mineral oils that were used back then? Or does it have something to do with the actual engines back then going through the oil quicker?

My final question is, could I increase the oil change intervals on a 90's Camry to say 15k if using a high quality A3/B4 or API SN full synthetic instead of a mineral oil?


Edited by antik (04/20/17 11:31 PM)

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#4384737 - 04/20/17 11:38 PM Re: Older cars = shorter oil change intervals, why? [Re: antik]
BrocLuno Offline


Registered: 09/06/15
Posts: 3418
Loc: Kalifornia Kollective
Well, 15,000 km is still roughly only 7,500 miles and that is entirely within the range of todays best dino and most synthetics.

The 1990's was prolly a transition period when refiners were still working out syn-blends and car MFG's were worried that owners would be putting the cheapest oil in there. Not a good situation for long mileage runs ...


Edited by BrocLuno (04/20/17 11:40 PM)
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#4384748 - 04/21/17 12:09 AM Re: Older cars = shorter oil change intervals, why? [Re: antik]
TallPaul Offline


Registered: 10/22/03
Posts: 13114
Loc: By Detroit
I think there was a day when they changed the oil every 1000 miles. And once upon a time (Model T days) they would put very thin, practically kerosene, in the crankcase for winter, else they would end up building a fire under the oil pan in order to start it. Back in the early 1900s oil got very thick in cold weather.
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#4384750 - 04/21/17 12:18 AM Re: Older cars = shorter oil change intervals, why? [Re: antik]
joemo Offline


Registered: 02/02/15
Posts: 24
Loc: mo
My 55 olds manual called for oil and filter change and grease every 500 miles.
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#4384751 - 04/21/17 12:18 AM Re: Older cars = shorter oil change intervals, why? [Re: BrocLuno]
CR94 Offline


Registered: 03/20/16
Posts: 347
Loc: Western S.C.
Originally Posted By: BrocLuno
Well, 15,000 km is still roughly only 7,500 miles and that is entirely within the range of todays best dino and most synthetics. ...
Did you mean roughly only 9,500 miles? (9321, to be more exact)

At least in the US, car manufacturers approved change intervals well over 5k-7k long before the 90s. It was 7500 miles [about 12,000 km] for my 1981 Mazda, and that wasn't new or extreme then.
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#4384753 - 04/21/17 12:28 AM Re: Older cars = shorter oil change intervals, why? [Re: antik]
spasm3 Online   content


Registered: 05/30/10
Posts: 7337
Loc: North Carolina
My 93 olds manual calls for 7500 miles non severe. Some toyotas were 10k miles in the 90's.
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#4384767 - 04/21/17 01:49 AM Re: Older cars = shorter oil change intervals, why? [Re: antik]
jongies3 Offline


Registered: 03/11/16
Posts: 443
Loc: MT
Technology has improved and engines are cleaner and more efficient than ever, that's why they can go longer on an oil change. Things are a lot different now than they were 20 years ago believe it or not! Not to mention as others have stated, oil quality has come a long way as well making it even more doable.

Back in the Model T days, it wasn't uncommon to change the oil every few hundred miles, no oil filter on those engines. But, with a top speed of only 25mph, it took a long while to rack up some miles on one of those babies I'd imagine! Haha
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#4384773 - 04/21/17 02:00 AM Re: Older cars = shorter oil change intervals, why? [Re: antik]
FordCapriDriver Offline


Registered: 10/22/15
Posts: 1728
Loc: Balearic Islands , Spain
My 1975 Ford Capri recomends 6000 mile / 10.000Km oil changes using Mineral 20W-50 oils, that is fairly long for the mid 70s and using API SE oils.
Nowadays longer oil changes are possible thanks to improved oil technology which has evolved a lot if you compare it to what was available 25 years ago, also modern fuel injected cars don't contaminate the oil as much with fuel as carbureted engines do, specially when warming up, modern ignition systems are better and more powerful which also means more complete and cleaner combustion.
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#4384775 - 04/21/17 02:01 AM Re: Older cars = shorter oil change intervals, why? [Re: joemo]
Kuato Offline


Registered: 10/23/05
Posts: 6404
Loc: Colorado
Originally Posted By: joemo
My 55 olds manual called for oil and filter change and grease every 500 miles.



Great example. Oils and engines have come a long way in the last 50, even the last 20 years.

If I had a 90s vehicle now, I'd do a UOA and see what the OCI could be extended to.

Oh, wait I kind of already did that with my '00 Jeep Grand Cherokee....up to 12000 miles on Amsoil, UOA said it could go further, and the manual called for 6000 miles for normal change, 3000 severe.
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#4384779 - 04/21/17 02:56 AM Re: Older cars = shorter oil change intervals, why? [Re: antik]
DemoFly Offline


Registered: 06/03/12
Posts: 965
Loc: Bremerton, WA
Oiling systems were a lot worse on older cars. Especially pushrod engines.

OHC engines have pressurized oil fed to the heads directly. Oil flow, specifically head flow, has both lubrication benefits as well as cleanliness benefits.

Clean engines produce less wear, it's just a fact.

Oils are also much better, too.
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#4384781 - 04/21/17 03:21 AM Re: Older cars = shorter oil change intervals, why? [Re: antik]
turboseize Online   content


Registered: 09/26/14
Posts: 170
Loc: Germany
The fact that fuel delivery has greatly improved and that fuel dilution upon cold start could be much worse in carburetted car than with port fuel injection has already been mentioned. But there are also two other factors.


In the 1980s, there was a sludge epidemic (probably due to not-very-good VII), which lead some manufacturers to order shorter OCIs. Then, most modern engines keep oil temperatures much better under control. Take my 1985 Saab, for example. Although equipped with an oil cooler, you can easily get oil temperature in the sump to more than 130C (turbocharger not water-cooled). Do that few times to a mineral oil with cheap VII, and it's toast. One spirited drive home for the weekend (600km in 4 hours or so, which means that to make up for all the construction sites and speed limited areas, you have to really drive flat out on any unlimited stretch), and a fresh semi-synthetic will be pitch black and idle oil pressure drops and you will have burned nearly a litre of oil in one single night. A fully synthetic, subjected to the same treatment, still looks new (and you will just loose 0.25 litres on such a drive).

Or take a buddy's Saab 99. 2-litre naturally aspirated, a single carb, only 100hp. But no oil cooler. Also relatively short geared, so high rpm in 5th gear. Having fun on a trackday or on a serpentine road, or just commuting on the Autobahn, this engine sees the same temperatures as the abovementioned turbo under full boost.
On the other hand, a new Golf VI GTI will keep the oil around 100C, no matter what. Only once have I seen oil temperatures of 125C, and that guy drove like a madman, digital throttle and always to 6000rpm before shifting. (Driving was slightly on these kinds ofroads, but quite fun and fast.) But even then, oil temperature peaks not exceeding 125C at basically full load, rev limiter is a different story to 135C when just cruising down the Autobahn at a mere 150-160km/h with the Saab 99...

So, it's basically two reasons:
1) average oil quality has improved significantly
2) modern engines are easier on the oil (port fuel injection and better temperature management).

But even one of these would be enough to greatly extend OCI. I have two Saab 900, one 900 turbo 16 from 1983 (Bosch LH jet electronic fuel injection), which was my daily driver until last autumn, and a 1983 900 GLE automatic (Bosh K-jet mechanical fuel injection and a 3-speed automatic, which means absurdly high rpm). Manufacturer recommend OCI is 7500km for the turbo, 10000km for the GLE (severe service cuts that in half).
With my driving style, that is mostly long-distance commuting at moderate speeds and a few drives for drivings sake, and perhaps one full-throttle 600km-run over an OCI, at 5000km any semi-synthtic 10w-40 were toast. Pitch black, but more importantly the 16V turbo would develop lifter tick when hot, the 8V automatic piston slap. That tells me oil has thinned out considerably. (Unfortunately, I never did an UOA back then, so I can oly judge the oil indirectly.)
With synthetic 0w-40, and driven the same way, after 10000km the oil looks new and UOAs show that it was indeed nearly virgin and I could have run the oil MUCH longer. That is still the very same car from the early 80s that killed a semi-syn in sometimes less than half the distance.




Edited by turboseize (04/21/17 03:29 AM)
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#4384793 - 04/21/17 04:55 AM Re: Older cars = shorter oil change intervals, why? [Re: antik]
KL31 Offline


Registered: 06/03/16
Posts: 294
Loc: South OZ
It's mostly the far superior oil now compared to 15-20 years ago.

I'd go one full year on a full syn. If you manage 15,000kms in that time then it will probably be fine.

Newer engines are definitely not easier on oil at all. Direct injection turbo is not as easy as port injection on the oil.


Edited by KL31 (04/21/17 04:55 AM)
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#4384816 - 04/21/17 06:28 AM Re: Older cars = shorter oil change intervals, why? [Re: antik]
Astro14 Online   content


Registered: 10/10/10
Posts: 7457
Loc: Virginia Beach
It's amusing to read what folks think "newer" means...

So, port fuel injection is "old"?? While GDI is "new"?

OK...I was thinking that updraft carburetors were old, while downdraft or side carbs were new...and that's when oil change intervals were 500 miles and you might want to pull the head for a "decarbon" every 500 miles, too.

But since it's a flat head, it's quick...

Look, oil has become much better, fuel dilution has become far less of a problem with better engine management, and engines simply run cleaner.
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#4384818 - 04/21/17 06:32 AM Re: Older cars = shorter oil change intervals, why? [Re: antik]
OneEyeJack Offline


Registered: 09/14/10
Posts: 6237
Loc: S California

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#4384819 - 04/21/17 06:32 AM Re: Older cars = shorter oil change intervals, why? [Re: Astro14]
demarpaint Offline


Registered: 07/03/05
Posts: 27385
Loc: NY
Originally Posted By: Astro14
It's amusing to read what folks think "newer" means...

So, port fuel injection is "old"?? While GDI is "new"?

OK...I was thinking that updraft carburetors were old, while downdraft or side carbs were new...and that's when oil change intervals were 500 miles and you might want to pull the head for a "decarbon" every 500 miles, too.

But since it's a flat head, it's quick...

Look, oil has become much better, fuel dilution has become far less of a problem with better engine management, and engines simply run cleaner.


thumbsup I'm sure the EPA had a hand in it too, along with mfgs. wanting their vehicles to be a little less costly to maintain.
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