[Big Dave]

I use synthetic oil and a bypass filter.

Never noticed it to improve fuel mileage but I do go two years between oil changes. The lab says I'm discarding good oil but 30,000 miles on oil makes my old-school nerves hurt.

But a 14 quart oil change with pricey synthetic dictates oil changes are not something you want to do real often.

BTW: 322,000 miles and no wear metal showing in oil analysis.