marlinspike

I'm on a temporary fuel injection system for a few months. The best I can do with this is a 0.91 lambda when cruising (so ~12.9:1AFR). Is this so rich that you'd worry about fuel dilution of oil?

Fabrik8

You can change your oil more frequently, which always helps a lot. A lot of fuel can evap out of the oil if you're not doing short trips too, so if you're getting everything nice and hot for a while that tends to help too. Dilution depends on a lot of factors with the engine though, and if you've got that Merc V8 you have a lot of cylinder surface area to keep clean of excess fuel.

marlinspike

Ah, ok. Well, it's a low detergent oil so I change it every 3000 miles anyways. I pretty much never drive less than 7 miles unless the engine was already hot to begin with, and rarely am I below 55mph. And pretty much every week I do one 30 mile drive, mostly on the interstate, and then 30 miles back. But yeah, it's a 5.6 liter V8.

I guess I'll just keep an eye on the feel and smell until I get my digital controller for the fuel injection back. On this mechanical controller I can only get a difference of ~ 0.03 in the lambda between full throttle and cruise (i.e. if cruise is 0.91 lambda, full throttle is .88, though for some reason above 5500rpm the lambda drops to 0.80)