Oil question

[Ron61]

My stroker that was built in 1996 was broken in on the dyno with 20-50 Valvoline racing oil and I have used that ever since. My question is this. My big block 1969 Cobra was broken in and has been running with Valvoline straight 40 weight racing oil ever since 1969. Both motors are as clean as they can be inside and I was wondering if I could switch the big block to the 20-50 so I don't have to keep two different cases of oil around. It isn't any problem but I was just wondering what some of the guys that are really in the know think about the possiblity of going to the 20-50 or should I stay with what has worked for 33 years.

Thanks,

Ron

[ST]

I've been using Valvoline 20-50 for the last couple of years in my car with great results.
Temps out here do get a little warm in the summer time but so far so good.

[Cal Metal]

Most people in the know--and I am certainly not one of them when it comes to oil--will tell you not to rotate between multi viscosity and single weight oils. Most of the experts on this topic are even more wary of "divergent" multi viscosity oils (10-40 v. 10-30). Most will not recommend using 10-40 oil because it takes so much in terms of additives to get the oil to protect and, also, flow at those numbers, that lubrication quality becomes more of an issue when using a 10-40 v. 10-30

This comes from a lot of literature on the subject, much of it having been talked about on this forum.

[Ron61]

Thanks guys,

I thought you shouldn't change from a single viscosity to multi viscosity oil and I didn't. The reason that I use the 20-50 is that is what the company that built my stroker used to break it in and I called them and they told me to keep using it. I have ran it since 1996 with no problems. I do check everything quite often and I change the oil more than is really needed. Our summer temperatures around here no longer get nearly as hot as they did 25 years ago. Now we just run from around 105-115 degrees but the humidity has really gone up. I remember days many years ago when it was up to 122 degrees but no humidity. This humidity is getting nearly as bad as in Georgia and some of those states any more. Thanks again,

Ron

[jdean]

I have seen some 0-30 synthetic recently. I wonder how they got the "0" designation for cold flowing ability.

[Cal Metal]

The 0-30 synthetics flow like water. Even in climates like ours--northern Wisconsin--no one recommends it. A case of too many additives substituting for too little lubrication.

[chopper]

I'm sure you will get a thousand opinions on this, so I thought I'd drop my two pennies on the pile. Like Ron61, I use 20W50 Valvoline in my engine on instruction from the builder. I have always shied away from straight weight (such as 40 weight) racing oil because I have been told by folks smarter than I that it typically lacks many of the longevity and anti-corrosive additives of normal street-engine oil. That's because the refiner assumes you're going to change the oil after each race, and so it doesn't have to last very long (from a chronological point of view). Also, unless you have a pre-oiler installed on your car, the startup wear on the rotating components may be rather high until the high-viscosity oil warms up and begins to flow.

As to the protection capabilities of 10W40, I can only relate my personal experiences of driving a 1970 Vette 350-350 for about 12 years and accumulating 140,000 miles. The car was driven in weather between Florida summer heat and Ohio winters during the time I owned it. I used Quaker State 10W40 Deluxe exclusively on that engine, changing oil and filter every 3000 miles. At 95,000 miles, we broke the engine down for a freshen-up, and could still see significant portions of the original honing marks on the sides of the cylinder walls. The marks were worn off in the center of the stroke, but could clearly be seen over the upper and lower 1/3 of the stroke. I agree that the 0W multi-vis are probably not suitable for most areas of the lower 48, but the 10W oils are OK for most applications. My opinion and experience, FWIW.

[Mr.Fixit]

I don't know what the lubrecation guys will tell you, but i have swapped viscosity, brands, mineral to synthetic, back to mineral, single vis to multi vis, on the same motor with no ill effects. I have even mixed brands, weights, etc within the same oil change. I usually break motors in on straight 30 non-detergent valvolene. Then after that case gets used up, I change to the 20-50 racing oil. There may be reasons not to do this, but they haven't hurt any of my motors yet.

[Bob In Ct]

Be careful about advice from mechanics and engine builders. A good friend of has been working on cars since the 60s. He says you should never change the oil or transmission fluid. He says "they get used to each other"! He also smokes like crazy, "when it's your time, it's your time" he tells me.

You can always find a builder who recommends non-detergent, straight weight paraffin oil. I'll bet the majority of race cars, however, are running on multi-viscosity synthetic oils. Porsche, Corvette, and others would not use them if they didn't do the job.

Bob