The other cost savings thing I do with cars is use synthetic motor oil. As a chemical engineer, I'm quite familiar with synthetics and lots of myths about them. I have my oil changed about every 12-15k miles at a quick change shop. I buy a 5 qt container at Walmart for under $20, so it costs me $37 per year for an oil change Vs ~$100 using conventional change intervals. In addition to the obvious cost savings Vs changing oil every 3500 miles, I get about 10% better gas mileage, better cold starts, less engine wear and reduce my environmental footprint. I've driven every one of my 12 cars over 200k miles and never had an engine problem.
Synthetic oil is used exclusively in high performance applications and has the following benefits:
- better low and high temperature properties
- better fuel economy
- resistance to build up of sludge and engine deposits
- there are no "natural" compounds (like sulfur which breaks down into sulfuric acid) to damage your engine
- extended change intervals