[BillT]

Most organic compounds are non-polar, which is why oil and water don't mix. Esters have a non-polar component and a polar component, making them soluble with a variety of other compounds. They also tend to have improved 'sheeting' properties, meaning they leave a film behind. In other words, a thin film of this type of oil stays on the cylinder wall long after you've shut the engine down.

 

[BillT]

Double ester oils are probably the best thing on the market now, but any major brand full synthetic should protect your engine for 6000 miles, and a semi-synthetic for at least 3000 miles.

As for me, I put Mobil 1 in Speedy, with a K&N filter (safety wired to the drain plug).

I posted an article a while ago from a guy who wrote a really good piece about oil, and he recommended Shell Rotella 'T' fully synthetic - available at most Wal-Marts for under $20 a gallon. The important thing is not to use 'energy conserving' oil (additives could cause clutch slippage), get the right viscosity index, and make sure its got the latest API rating (SL or later)

Also, the filter is the same as the small filter most companies (Fram, Wix, Purolator, K&N) make for the Mazda V6.

I think my next filter may be the K&N (I think #1009) for the Mazda. It's about an inch longer, and still has the safety-wireable nut on the end for easy removal, and is about $5 cheaper, because its not a motorcycle filter.