Originally Posted by Mad_Hatter
Originally Posted by RDY4WAR
A straight grade will have a higher HTHS and higher pressure-viscosity coefficient (most of the time), both which provide more high temperature protection but also increase hydrodynamic drag. For these guys, a 0.5% power gain is far more important than a little less wear.
EDIT: As mentioned above, they are straight grades essentially. No VI. They use some of the "lightest" base oils they can find though.
Ok, that makes sense for a top fuel funny car or pro stock bike but NASCAR does have hp limits (restrictor plates) add to that these engines don't have a problem producing hp..in fact it's just the opposite, they create too much hence why NASCAR restricts hp.
NASCAR
NASCAR restricts air flow into the engine. You're limited on how much air and fuel you can burn so the only other way to make power is to free up power with better mechanical and thermal efficiency and less friction.
NHRA Top Fuel and Funny Car doesn't actually care about that. They use an SAE 70 grade mineral oil to handle the massive amount of pressure as well as handle the high fuel dilution. Those engines consume over 6 gallons of nitromethane every round and some of it inevitably ends up in the crankcase. It's not uncommon for those engines to have 10+% fuel dilution at the top end of the track. When the entire engine is torn down after every run, it doesn't really matter. They are also making way more power than they can use anyway. It's less about who can make more power and more about who can put more power to the ground without spinning. They can't fully lock up the clutches until past half track. It's not like Pro Stock where they are fighting for every last hp to get a competitive edge.