My 300D starts and runs, then after a while the car slows to less than 5mph and continues to run at that speed. Then out of no where it takes off full speed ahead. Runs for a while and repeats the process again and again. Is this a fuel delivery problem? It has been run on a blend a few times this passed summer.

I also have an oil leak that coming from some where by the air filter. If I put 5qts in drive less than 40miles and the oil shoots out every where its a mess?

Any ideas?