Just curious you all. To everybody who owns an Iron Duke powered Fiero, and lives in an area that gets real hotttttt. What grade motor oil do you run ?

5w-30 all of the year regardless of weather.
Maybe use 10w-40 but only in summer in most places.
Do Not use 20w-50 and other heavy oils.

Syn Oils won't cause a leak in a engine in good shape.
Many current oils not just syn oils can wash out crap blocking leaks.

See my Cave, Oil and Filter
and https://www.api.org/product...ents/motor-oil-guide for current guide

Note: Many new cars are labeled on engine for 0w-20 but when you read OM etc 5w-30 is still allowed under Warranty.
0w-20 and now 0w-16 are mainly to get EPA CAFE points and related BS rules in EU and so on, not to help you or to make cars last.
Just read OM before using 5w-30

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

I don't own an Iron Duke, but I'll say something anyway...

I think that the oil requirements would depend on what year of engine you have.

The Duke started with a flat tappet camshaft, but then switched to a roller cam for 1985.

If you have the flat tappet cam, then you'll want an oil that will help prevent wear at the lobe-to-lifter interface.

If you have the roller cam, the requirements are less stringent.

quote Originally posted by pmbrunelle: I don't own an Iron Duke, but I'll say something anyway... I think that the oil requirements would depend on what year of engine you have. The Duke started with a flat tappet camshaft, but then switched to a roller cam for 1985. If you have the flat tappet cam, then you'll want an oil that will help prevent wear at the lobe-to-lifter interface. If you have the roller cam, the requirements are less stringent.

Any recent API S_ specs allow less zinc phosphorus etc.
This is so the Cat(s) last longer and other reasons.

Can try adding "anti-wear" additives to the oil for flat tappet engines but no guaranty any will help. Worse, some won't work and may plug up the filter or cause other problems.

Now API has SP that supposed to work better w/ E-gas and more. (API is skipping SO) see api link above.

https://www.hemmings.com/classic-oil/10w30

Something like this is formulated for older cars with higher levels of ZDDP. Might be a good choice.
But I agree with Orge, don't use anything thicker.

The API limits are more lenient with a hot viscosity of 40 vs 30.

La Fiera suggested this oil to me for use with my Fiero engine (flat tappet):
https://www.fiero.nl/forum/F...L/142133-5.html#p169

Here is adds that the Liqui Moly oil contains the required zinc/phosphorus:
https://www.fiero.nl/forum/F...L/142133-5.html#p171

So with this oil, it's supposed to be good out of the bottle. No need to play chemist and risk adverse reactions by mixing mystery liquids!

That Liqui Moly oil complies with API SL.