Would running one quart low make more horsepower?

Not open for further replies.


Staff member
May 27, 2002
Guelph, Ontario
I've always been curious if running my engine one quart low on oil when I go dragracing would make more power? Have any of you guys that have built race motors in the past experimented with this? I thought this might provide gains similar to a windage tray, where the lesser amount of oil prevented a drag on the crank, freeing up some power? I might just try it out one of these days when I do an oil change right before a drag event. I'll put in one quart less oil than usual, make three runs to establish a baseline and then top it up with that quart and make three more runs. My car is consistent enough that I would be able to see any changes in power quite easily. Does this sound like an idea, or am I being foolish? I'd never run it a quart low for too long.
There have been tests on this and running a quart low does make a few extra HP. I never add oil till it hits the quart mark, so I'm not afraid to run it to that point. I've never spun a bearing or cause any other problems, and I run my cars like I was making a drag run at least once a day...
I have seen where too much oil has hurt Hp. However, that doesn't mean running low gives you more Hp. Try it. Like someone said "nothing ventured, nothing gained". Besides, it's your motor not mine.
Patman, The easiest way to make more horsepower is to use a lower viscosity oil. You now find Winston Cup cars running a 0w-30 synthetic to do qualifying laps and then switching to a heavier grade (typically 20w-50) for the actual race. A thinner oil produces less "intrafluid" friction and less energy to pump. I've also seen motorcycles that dragrace using 0w-30 synthetics .... TooSlick
Ted, the one thing with running a lower viscosity is that I wouldn't have enough protection. With my method I could always continue using my 10w30, and just set it up so I'm a little low on oil whenever I drag race. So this method (if it works) is easier than switching viscosities around. Vader raises a good point, even when it's a quart low it's still in an acceptable range. Think of how many people are out there driving around at more than a quart low right now. I know people who somehow managed to run their cars with just a single quart of oil in there, and they top it back up and it runs for years to come. Of course not all engine designs can handle this, but I think an old school SBC like mine probably could, being a pushrod motor and all.
Running the oil level lower can definitely add some horsepower. It can help from churning up oil in the crankcase less too. This has been a 'hotrodder' trick I've been aware of for quite a while. As proof, and Patman maybe you know about this feature, when Chevy released the technical aspects of the LS6 they showcased a feature that reduces windage in the crankcase. The problem with the LS1/LS6 is it has a super shallow oil pan to help keep the engine short. One of the bad things is when the pistons push down, the underside pushes air along with it. With a lot less volume in the crankcase and oil pan to 'absorb' the pressure, it can rob some horsepower. As a solution, Chevy made the LS6 block casting with small slots at the bottom of the cylinder bores that connect to adjacent cylinders. With this setup the air being pushed down on the underside of the piston can be channeled into the cylinders next to it. Chevy has claimed that this feature gave 10hp that would be lost otherwise. I run my GN only about 1/4 of the way past the add mark on the dipstick. I also have a much bigger filter to keep the oil volume about the same as what would be factory full. http://www.rjcracing.com/RJC_Buick_Products/RJC__Biggie__Oil_Filter/rjc__biggie__oil_filter.html I posted the link to show; 'Yes, the volume with that setup would compensate for running about 3/4 of a quart low'. After running the oil level lower and putting in a good brass check valve in-line with the PVC valve(to keep boost from backing through the PVC system and into the crankcase), it takes a long time for the breathers on the valve covers to get saturated with oil. Before I did those changes, the breathers(I clean them at each oil change) would oil up pretty fast and one would actually start dripping off some excess after some hard running. I'm sure the gains and risks depend on the engine and other factors but there's no question to the theory of having more air volume in the crankcase.
Interesting stuff Kernel! I'm running a larger filter too, although this filter probably only holds an extra 1/4 quart over the stock one.
Not open for further replies.