Why 10w30 for High Performance Engines?

Joined
Jun 9, 2018
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Austria
Hello! I have done a lot of research in the past and always came across one fact in the USA. That car manufacturers always recommended 10w30 instead of 5w30 for high horsepower engines! For example:

1. Jeep recommended in owners manual for 4,7l V8 5w30 and for the 4,7l V8 High Output which had about 30 hp more they recommended 10w30

2. Tuning magazine recommended owner of Dodge Neon SRT Mobil 1 5w30 if driven normal and Mobil 10w30 when driven hard!

3. Genuine Mopar oil in the 90s was 10w40 Sj rated, 10w30 Turbo approved for high performance engines and 5w30 All Season fuel efficient

4. Gm recmmended for Trans Am Turbo at the beginning of the 80s SF rated 10w30 and 5w30 for low temperatures

My question is if anybody knows why manufacturers wanted in their High performnce engines an oil which didn´t flow as fast as 5w30 would and why the didn´t recommend 10w40 which would be more thick than 10w30 in high temperatures which occur in high performnce engines! I´m talkiing bout times when synthetics weren´t that common in the USA!

HEre in austria we had at the beginning of the 90s the synthetic oil wave, when every oil manufacturer began to offer full synthetics in 5w40 and 5w50 and castrol even offered a 10w60 which were used in in multivalve and turbo engines!

Does anybody have an answer, would be very interested!
 
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You are quoting old data. Why not check what Chevrolet recommends for their 2022 Chevrolet Corvette or what Stelantis recommends for their Challenger Hellcat. The answer is they both specify 0w40 motor oil.
 
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Astro14

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Because 30 years ago, the VIIs used to make a 5WXX or 0WXX were prone to breaking down and 10WXX had fewer of those VIIs.

Things have changed in thirty years.

You’re not pumping the gas twice on a cold start to set the choke and get a few squirts from the accelerator pump into the manifold any more, are you? 😉

Because that’s what I was doing thirty years ago, with my 10w30 or 10w40 in the crankcase of my carbureted V-8s…
 

4WD

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It’s not just the star polymer VM’s changing the game - formulator types have many base stocks to combine these days - and can alter the VI and other targeted performance parameters that way as well …

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It all depends on what the application is. Remember that the EPA dictates MPG standards and the manufactures have to compromise MPG with engine life.
5w-20 will get you the best MPG but shortest engine life under high load and high rpm. So the compromise? 10w-30.
They assume that you are going to be running the engine hard some of the time but not all of the time.
If you are going to track days you need to use a different motor oil entirely.


But just running the kids to soccer and wanting to hit the throttle hard from the stop light every once in a while? No need to run a track oil that will not shear quickly and can handle the high heat and rpm of such demand.

If it were not for CAFE demands and EPA standards these ultra thin motor oil’s would not be a thing.
Your engine needs to get max MPG from stone cold in -0 temps to all operating ranges.
They have no idea how each person is going to use their vehicle, so they have to average everything out for the masses, and the masses are asses.
Tire PSI…average…oil change intervals…average…motor oil grade…average…even transmission and power steering fluid is a low viscosity now to increase MPG.
 
Joined
Nov 27, 2017
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Because 30 years ago, the VIIs used to make a 5WXX or 0WXX were prone to breaking down and 10WXX had fewer of those VIIs.

Things have changed in thirty years.

You’re not pumping the gas twice on a cold start to set the choke and get a few squirts from the accelerator pump into the manifold any more, are you? 😉

Because that’s what I was doing thirty years ago, with my 10w30 or 10w40 in the crankcase of my carbureted V-8s…
This
 
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