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What weight oil to use.


Guest sintid58

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Guest sintid58

I was wondering if I should use a heavier weight oil in my 455. It runs very warm, espescialy on long trips and I am thinking of using 20/50 on the long drive to Flint, or would 10/30 work as well. Any one that drives one of these knows how hot the engine compartment gets when you are driving them. Hard to even pull the dipstick at fuel stops.

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Guest imported_SKYSTHELIMIT

I just seen this new product in the local auto parts store but I forget the name of it. Its a small bottle of this stuff that you add with your oil and its suspose to lower the oil temp by 50 degres. Don't know if it works though never tried it myself. The next time I get down there I'll get the name for you.

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I don't know if you want to go as high as a 20/50. This oil was never recommended. I had a 455 and know how hot that engine ran. A good 10/40 should protect your engine. The heat will only be a factor in bumper to bumper traffic. I would be more inclined to checking your cooling system to make sure its up to specs. Just a thought.

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In the late '70s or early '80s, GM put out a tech bulletin to not use 20W-50 oil in their engines. The reason listed was that the viscosity improvers could stack up behind the rings and cause the rings to stick. When I questioned our Pennzoil rep about that (as I'd already logged over 100,000 miles+ in with my 305 Camaro at that time with no problems on 20W-50 Castrol), he replied that in their routine testing of oils, that GM found that problem with possibly one brand of oil so they had to make a blanket recommendation against all of them as they couldn't say "Don't use ______ oil" in their service literature.

In the earlier '70s some manufacturers would allow 20W-50 if the ambient temps were consistently above 90 degrees and under sustanined speeds of 75+ mph, in other words, high speeds with heavy loads. As oil technology and ratings have progressed, that recommendation might not be applicable today. Now, even in their heavy duty rated one ton pickup applications, the GM recommendation is 10W-30 and the diesels are 15W-40 with only a few car motors recommended at 5W-30.

In more modern times, the 10W-30 oil is now listed as "fuel conserving" whereas the heavier weights aren't. If the bearing clearances and such in your earlier motors are still in spec, there probably would not be any real benefit to using 20W-50 in place of 10W-40, I suspect. Using ANY viscosity improver additive with one of the heavier multi-weights is not recommended either!

I suspect the main reason that 10W-30 or 5W-30 is currently recommended has more to do with decreasing the amount of power used to drive the oil pump in the engine and how quickly the oil flows after startup. These things can have an impact on the modern computer controlled engines, I suspect. Plus, if they use 10W-30 oil to run the emissions testing and fuel economy testing, that's what they have to recommend be used by the customer.

My main concern would probably be making sure the complete cooling system is in good shape (the block passages and the radiator and fan clutch and shround and such) plus maybe putting a few degrees of additional spark advance in the motor (and making sure the vacuum advance is working). By design, the emission controlled motors typically ran a little hotter than their higher compression ratio counterparts to help have higher exhaust temperatures to continue "cooking" the emissions in the exhaust manifold and such. Just going from a rated 9.2 compression ratio to 8.2 will significantly increase exhaust gas temps at the end of the tail pipe. Engines with their spark timing specs retarded from optimum also resulted in higher operating temps. I suspect that some attention in these areas might help your heat concerns.

To me, a quality 10W-40 regular oil would be as thick as you'd need to go if you desired a little more heat protection. Upgrading to the same brand of blended synthetic 10W-40 or 10W-30 oil that you're presently using would be an option too. It's possible that the blended synthetics might be a little slicker and might remove a little of the friction induced heat as a result, but if that amount of heat is significant, then you'll soon have other situations to address with the engine, I suspect.

If the engine is running at 200 degrees, the oil temp will typically follow that temp after about 10 miles of driving. That's still about 70 degrees before oil degradation due to heat will start happening with normal oil (i.e., not blended of full synthetic).

As for auto supply "wonder" additives, if you start with a quality oil of the correct viscosity, you should not need anything extra to add to the oil. Years ago, a customer had a Pontiac 400 that had some bearing noise. He changed the oil and put 20W-50 in it with one can of STP. He then added another can of STP to that mix. We sold the repair shop that got the car a new crank and set of bearings. It had been acknowledged that one can of STP would raise the upper viscosity level by 10 numbers. In that case, he ended up with 30W-70--might just as well have put rear axle lube in there.

Just some thoughts . . .

Have a great trip to Flint!

NTX5467

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NTX's "post" about oils, ( and his cautions about adding "mouse milk" or other violations of engine manufacturers ) are, I believe SOOO terribly important to the operation of ANY car, "collector" or not, I hope he sees this...

"NTX....YOUR POST IS SO GOOD, AND SO IMPORTANT...I HOPE YOU

OR SOME OTHER COMPUTER BUFF FIGURES OUT A WAY TO COPY YOUR

'POST' AND GET IT INTO ALL OF THE FORUMS FOR ALL CAR BUFFS TO SEE..."

pfh

(Perfedious Reindeer Hunter)

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