Can an Oil Change Affect Horsepower?

A lot of people have asked this question before and the jury has been out on whether this is something that is true or not. We have attempted to test to see whether certain brands of high-quality oil have a gain in power over others before with mixed results. Our dyno tests have always been inconclusive with the differences being too small to be considered or perhaps caused by variables such as differences in viscosity or sump level.

One of the things here is all of our cars in our fleet all run with some sort of premium performance synthetic oil in the pan.  We think that perhaps we have proven that when all else is equal there isn’t much power difference in power output between one brand of premium synthetic oil to another.

Believe it or not, we have never dyno tested the difference between regular dino oil and a premium synthetic on our dyno before, so we decided it was time to see!


Our test subject is the shop beater, Project EP3 Si. Its wheezy K20A3 engine is the subject of contempt around here since the car has the questionable honor of the being the slowest car of the MotoIQ fleet.

Fortunately, it also gets the best mileage and it holds a lot of gear, so it gets driven a lot running cameras and stuff to the track and back. The EP3’s engine also gets neglected because, well, it’s slow. Because of this, it gets fed regular dino oil bought in the AutoZone sales bin that also goes in the lawn mower and generator.  We at least got the right gas saving 5W20 viscosity for it most of the time.


To start our test, we strapped Project EP3 to our stingy Superflow dyno and laid down a very surprising 120 whp and 114 lb/ft of torque.

What was cool is that the neutered by the factory K20A3 engine made its peak torque at 2400 rpm and had a nice flat torque curve all the way to the 6800 rpm redline. Everyone loves to hate on the poor A3 as the retarded step-brother of the A2, but it does have its merits.


To make sure we had as close to equal oil levels for the before and after test, we checked the oil level right after our dyno runs.

We have found that the oil level and associated windage losses can make a few hp difference on the dyno, and since our anticipated power gains will be small, we wanted to make sure that this would not be a factor.


To be honest, no one around here could remember the last time we changed the oil in the EP3. However, the oil on the dipstick didn’t seem that bad.

It could be that the thin 5W20 that is the recommended factory fill burns faster, and we would occasionally have to add a quart which kept the oil on the fresh side!


Leave a Reply

Your email address will not be published. Required fields are marked *