A friend of mine who drag raced a GTO in the 70's for many years told me the other day that when I get my rebuilt Duke running and I use a high zinc break in oil or a high zinc break in additive that I should just run straight 20w 50 racing oil. He has been doing that in his 199-something Dodge Dakota since new. He said that truck has 200,000 miles on it, has oil pressure like it did when new, and is super clean inside. Any thoughts on this? Or is he nuts?

Thanks

Curly

Run GM recommended oil... 5W-30. I had a Formula with 200K, but ran 5W-30. Oil pressure was 70PSI.

Motor Oil 101 ... It's a long read, but well worth your time if you want to learn.

What problem(s) do you have running the GM-recommended oil spec that you or your friend expect to avoid running 20W50 racing oil? A thicker-than-spec oil will provide reassuringly high pressure on the gauge, but possibly at the expense of adequate oil flow to the cam, main, and rod bearings. Wear at cold start, where more than 80% of engine wear occurs, will be higher with a 20W oil than with a 5W oil. Finally, the additive package in a good "racing oil" will have typically more extreme-pressure, anti-oxidant, and anti-foaming components, but it will have less of the anti-corrosion, detergent/dispersant, and acid-neutralizing components. By its very definition, true racing oil is designed to be changed often ... as often as every race.

My recommendation for a street-driven Duke would be whatever GM recommends. If you want extra protection, use a 100% synthetic (e.g. Mobil 1) in the GM-recommended viscosity range. That said, I did use petroleum-based 20W50 Valvoline Racing Oil in my old Porsche 928, and the original engine was still clean, healthy, and strong at 195,000 miles. IMHO, good preventive maintenance and regular oil and filter changes are far more important to an engine's longevity than the specific oil you use. In my Fiero (2.8) I run Mobil 1 5W30, and I change the oil and filter every 10,000 miles or once a year ... whichever comes first ... whether it needs it or not.

[This message has been edited by Marvin McInnis (edited 09-13-2011).]

That's a bit much for a daily driver. If you were racing on a regular basis that might warrant it but I doubt the duke could stand up to the kind of punishment that viscousity is intended to dampen, not to mention the increased startup wear you would incur from the increased amount of time it would take to move that sludge on a cold start. Note the manufacturer trend now is toward lighter weight oil and much of that has to do with the fluid dynamics of engine oil, quicker delivery to the bearings and only enough viscousity to support the intended use throughout the life of the engine. 10W40 in a pretty hot climate is as far as I would go on a daily driver.

I use Mobil 1 Turbo Diesel Truck 5W-40. It has all that extra good stuff, like zinc.

------------------
Turbo 3800 E85 5spd spec5
11.53@126.7

Racing oil worked well on the street in much older V8 engines where tolerances were quite loose. Todays engines are made to closer specs and 20W-50 racing oil could restrict oil flow and prove detrimental.
If you want a long lasting engine; break it in with the GM recommended standard weight oil for the first 5000 miles. Then switch to full synthetic oil of the same recommended weight. Use of synthetic oil with regular oil changes will make an engine last a very long time. A friend of mine uses nothing but Mobil 1 and has 230K miles on his V6 engine and it still meets compression specs, runs well and burns no oil.
I'm sold on the stuff.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, ZZP Intercooler, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Yep what you guys are saying was kind of my thought. I think once I have everything broken in I will use a good synthetic. That should keep things rolling just fine. Thanks.

quote Originally posted by Dennis LaGrua: Racing oil worked well on the street in much older V8 engines where tolerances were quite loose. Todays engines are made to closer specs and 20W-50 racing oil could restrict oil flow and prove detrimental. If you want a long lasting engine; break it in with the GM recommended standard weight oil for the first 5000 miles. Then switch to full synthetic oil of the same recommended weight. Use of synthetic oil with regular oil changes will make an engine last a very long time. A friend of mine uses nothing but Mobil 1 and has 230K miles on his V6 engine and it still meets compression specs, runs well and burns no oil. I'm sold on the stuff.

Pretty much agree with that. Ive used 50w oil in lots of my older cars during the hot summer. I just figure its a better 'cushion' for the bearings. Its like adding STP treatment. It never gave me a problem. If you know the history of the engine, Mobile 1 is perfectly fine, but do recommend synthetic. Its more stable and heat resistant than dino oil. I personally use Castrol Synthetic...old or new.

Thought experiment: What do you expect will happen if an engine is started with the main oil gallery totally plugged?

Answer: You will first feel all warm and fuzzy, because the oil pressure gauge will indicate more than adequate oil pressure. Eventually, sometime after the noise begins, you will realize that no oil is actually getting to the bearings or the rest of the engine.

Too-thick oil works in a similar way. The oil pressure at startup is reassuringly high, because the pickoff point is just downstream of the oil pump, but most of the oil is being dumped through the pressure bypass valve. Very little oil will actually be getting through the galleries and to the bearings until the oil warms and thins to normal operating viscosity.

It is interesting to note that many racing engines require that the oil be preheated before starting, to thin the oil to nearer the normal operating viscosity. With cold oil the starting pressure will be high, but the bearings may still be starved for lubrication.

[This message has been edited by Marvin McInnis (edited 09-12-2011).]

The first # pertains to the cold flow viscosity. The lower the #, the quicker the bearings will see oil after a start-up, so lower is normally better, especially in the winter months. 0 to 20 are the typical values.

The 2nd # pertains to the hot viscosity. The lower the #, the easier it flows, the less pressure you will see. The lower the number, the more fuel efficient the engine will be, but the number must be high enough to provide adequate hot idle, cruise and WOT pressure.

5W30 is a good compromise.

I run 10w40 in all of my V8 cars. 10w30 in my 2.8 when I had it and what ever was on sale for my wifes Saturn

I use to run 20w50 in my V8 but after I started driving it in the winter I changed to the lower weight. I use to run 20w50 in the summer and 10w40 in the winter but I wasn't putting enough miles on my car to justify changing the oil that much. I just use the 10w40 now and keep an eye on it. I do still change my oil in the spring just because of all of the condensation I know doesn't get the chance to burn off in the winter.

In a "Duke", all you will accomplish by running 50W oil is "Cutting the MPG, down quite a bit !"

quote Originally posted by Marvin McInnis: .... By its very definition, true racing oil is designed to be changed often ... as often as every race.....

This is a solid fact. Anyone running racing oil in their daily driver is plain old nuts. for two reasons. Wasted money on buying anything that says "racing" on it. and not using the proper oil for the engine.

it's like buying synthetic oil and changing it every 3000 miles.

[This message has been edited by timgray (edited 09-14-2011).]

quote [B]Originally posted by timgray:[/B it's like buying synthetic oil and changing it every 3000 miles.

I like that one ... and there are those that do it. I change my synthetic every spring/ 7500-10000 miles like manual says. I never have any engine oil related problems. I routinely get 150-200K before I trade for something else. I cant remember the last oil burner I owned.