ExxonMobil announced their sponsorship of Tony Stewart’s car for a partial 2011 season today. Glad to see Mobil1 staying in the sport – especially since ExxonMobil are huge, huge supporters of math and science education.
Got a number of questions today about how a team that uses Hendrick engines – Hendrick having Quaker State as a sponsor – can have sponsorship from another oil company. The questions were along the lines of “Will Stewart-Haas have to drain the oil pans when they get them from Hendrick?”
Here’s a quick answer, since I’m in the middle of a cross-country move and just about everything I own is in boxes:
NASCAR engines use a dry sump system. That means that (unlike a passenger car engine) there is no oilpan on a NASCAR engine. There are a couple of practical reasons for this. One is that an oilpan is an invitation for disaster. One bump on the bottom of a rough track and you’ve got a rupture. Given that the NASCAR engine uses 22 qts of oil, that would be a lot of oil spilled on the track and a huge fire hazard. You want to use as little energy as possible on friction, which means that the last thing you want is for your crankshaft to be spinning at 9,000 rpm through a pool of oil. NASCAR engines use squirters to get the oil where it needs to go. Removing the oil from an oil pan to a tank (located behind the driver) keeps the majority of the oil in a much safer location. The oil tank is surrounded by a metal shield because the oil becomes extremely hot and the vaporization of the oil molecules creates quite a smell. (The oil tank lid is what went missing a couple of years ago on the 99 car.) The oil tank cover is on the leftmost of the photo. The metal shield surrounding it is not shown on this picture that I took at the Hendrick Motorsports museum.
When a team gets an engine from another company, the engine is delivered dry. Although oil is composed of mostly oil molecules (duh!), a small fraction of the oil is non-oil additives. These molecules have different tasks – helping to carry away heat faster and more efficiently, sweeping away small bits of debris, reducing friction, etc. Each team chooses what kind (manufacturer, viscosity, etc.) of oil they want to use for qualifying and for the race. Teams with ‘technical partnerships’ with oil manufacturers work with the engineers from that company and have access to the information that company has about friction-reducing additives, anti-fouling chemicals, etc. The larger teams spend a significant amount of effort researching how different oil additives change the longevity, efficiency and temperature of the engine under different conditions (i.e. wide range of rpms, continuous high rpm).
There are non-technical issues as well. Perhaps a team is willing to lease engines to a second team that isn’t performing very well. Requiring them to use a particular brand of oil makes an implicit suggestion of endorsement by the oil company. When my book (The Physics of NASCAR) was coming out, we joked about taking a picture of a driver or two behind the wheel with the book. Then we realized that a couple of the drivers we were considering were running badly enough at the time that maybe it wouldn’t be the best publicity for the book.
Similarly, the oil company may not want to be seen to be endorsing that team. So decoupling the oil and the engines makes a lot of sense for technical, as well as sponsorship, reasons.
If you want to learn more about oil, come out and see the science of motorsports exhibit at the very first USA Science and Engineering Festival, October 23-24 in downtown Washington DC. Our booth will be about 13th and Pennsylvania. We’ve got a new hands-on demo exploring the properties of oil, including viscosity and clearance. Lots of cool things to play with, plus a couple hundred other exhibits, ranging from the nanoscopic to the entire universe. It’s going to be great fun and I hope to see some of the blog readers there.