I generally run multigrade oil in the racecar. Typically Amsoil Dominator 15w50 or Brad Penn PG1 20w-50.
I'm seeing more and more straight 60 weight racing oils. Some examples::
https://www.amsoil.com/p/dominator-sae-60-racing-oil-rd60/
https://vpracingfuels.com/product/vp-traditional-non-synthetic-racing-oil-sae-60/?c=393
https://www.onguardengineoil.com/sae-60-w-racing/
Any benefit for race-only use?
They keep methanol engines alive after all the fuel wash turns the oil into a watery emulsion.
Beyond that, straight weight oils are better for race engines because there are none of the plasticizers that make the viscosity "variable". That means less viscosity breakdown, and less foaming by a mechanism that I do not remember. 60 is probably overkill, if you have good oil pressure then 30 or 40 is plenty. Super thick oil mainly wastes power pumping oil through the regyulator bypass instead of past the bearings, which is how they stay cool.
I see exactly zero benefit to a straight heavyweight oil unless you're racing a 1000hp dragster with massive bearing loads. And of course the risk of not getting good pressure at cold startup. IDK what you race, but unless it's something pretty exotic/extreme I would stick with a 15w40 at heaviest. Also depends on your bearing clearances - thicker oil for bigger clearances, thinner oil for smaller clearances.
that said, I dump Rotella T6 from walmart into my competition rally car (and we use it in our BMW enduro car), and never have had any oil-related issues (except a smashed oil pan from a big rock....). I've never read anything that convinces me the extra cost of specialty oils is beneficial to anything other than the highest-strung race engines. YMMV.
That makes sense to me. I'm running Weber carbs, so I need an oil that can handle a little fuel contamination. I was looking at Motul 300v Le Mans (20w-60).
This is an old, high-milage engine. Heavier weights seem to give me less oil consumption. Maybe it's placebo effect.
irish44j (Forum Supporter) said:I've never read anything that convinces me the extra cost of specialty oils is beneficial to anything other than the highest-strung race engines. YMMV.
I can definitely see where you're coming from. It's just that the marginal costs are often pretty small: one gallon Rotella T6 is $30 at Walmart whereas a gallon of Amsoil Dominator is $44 through "preferred" dealers.
Considering how many thousands I spend on a summer of racing, that $14 bucks price difference hardly even registers.
I used to run straight 30, but that is getting harder to find at the FLAPS.
The plasticizers that make an oil multi-viscosty are not very good lubricants, and they are (IIRC) the primary source of oil breakdown in modern oils. So the old adage of keeping the viscosity spread as small as practical has basis in fact. That said, synthetic oil are naturally multi-viscosity, because the cold and hot tests were generated around non-synthetics. Which is where you see things like 5w60 and 0w60 oil. (IIRC 0w60 flows the same cold as hot!)
I'd run the lowest viscosity that maintains good oil pressure when hot and call it a day. More than that is just flowing oil though the pressure relief. (And if you are diluting with fuel, I buy gallons of 15W40 in bulk when it gets marked down to $10/gallon, and change it frequently)
My BMW runs 10w-60, but you have to carefully warm them up before revving them much (there is a gauge telling you when you can get on it).
I agree that there is no advantage to going over 50 in a race car and probably 40 on the street.
I've been running Castrol 15w-40 for a long time now, on the track and on the street. I haven't seen much problem with it, and it's $14/gal at Tractor Supply. Of course, I haven't done an oil analysis, either (but I really should).
If it's a dedicated race car that never gets driven below full operating temperature, a single-weight oil will last longer, but you should run your normal hot viscosity, in your case 50, not anything thicker. An in-between solution would be to run an oil with a smaller cold/hot viscosity spread like 25w50 or 30w50.
LanEvo said:irish44j (Forum Supporter) said:I've never read anything that convinces me the extra cost of specialty oils is beneficial to anything other than the highest-strung race engines. YMMV.I can definitely see where you're coming from. It's just that the marginal costs are often pretty small: one gallon Rotella T6 is $30 at Walmart whereas a gallon of Amsoil Dominator is $44 through "preferred" dealers.
Considering how many thousands I spend on a summer of racing, that $14 bucks price difference hardly even registers.
Jeez - At the Walmart here (and online) T6 gallon is regularly $20 and I can usually pick it up for $16 if I catch a "rollback" day. Since I use it in the tow rig, the Porsche, the Raider, and the rally car (which gets frequent oil changes for obvious reasons) that adds up. But even on the rally car alone, using Dominator would run me an extra $200/year or so. You may be more baller than me, since $200 pays for a couple rally tires for me :D
I guess it's just difference use cases. I only get to race 2-3 weekends a year. I don't drain the oil after every race: I'll flush and fill all the fluids at the start of the season and run them all summer.
So, I basically need 6 quarts of oil to get me through a "full season" (lol) of racing: 5 quarts in the crankcase and 1 extra quart to top off as needed.
In reply to LanEvo :
Must be nice. I change the oil in the RX-7 before every rallycross. I start out a quart low, by the time I drive to the event, run the event, drive home, then drive out the rest of the tank by commuting to work, the oil is a quart overfull. That's all gasoline taking up the extra.
I do change the filter once a year.
FWIW, the question about a straight-viscosity oil was discussed in part 2 of "Ask an Oil Expert."
I run walmart synthetic 10W30 in the Tib and used the 5W20 in the Forte and beat them mercilessly. As long as you're not sheering the vis and losing oil pressure, you should be fine.
I ran 10W30 Amsoil in the ZX2SR for the 10 yrs I owned it. On track days I beat it hard even in 90F. In winter it never failed to start at the ice races.
Then driven on long summer trips in summer heat.
Got changed once a year.
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