I just had my 500 efis rebuilt at 238 hrs. I broke a lifter. Bruce at express eng. Said everything but the lifter looked great. Everyone you talk to has a opinion What do you run? Im going to run mobil 15/50 again. 200 hrs wide open I think I showed them no mercy.

Thats good to hear Velocity Tom, I run the same stuff in mine, 224 procharged hrs

Good deal!

Why do you run 15/50? The factory calls for straight 40 weight. I have always run a single weight oil in my boats and I'm curious as to why you run the multi grade. I was going to start running Mobil 1 this weekend.

Mobil 1 does not advertise a straight weight synthetic. I believe this has been covered before but I believe I recall the explanation as the synthetics are straight weight that can effectively cover the listed weights.

I'm a firm believer of synthetic oils. Specifically Mobil1.
I've used it in our cars (past and present) for well over 300K miles. One car was turbo charged, we traded it in with 115K on it with no turbo bearing or seal failures. My previous truck had 155K on it with no oil leaks, no smoke, no valve problems.

Before I started using Mobil1 I read every available article and test report I could find. There were several un-official tests conducted by private individuals with surprising results.
After reading those I was convinced.

BTW Mobil1 comes in 0-30, 5-30, 10-30, 0-40, 15-50.
The 0-40 is available at AutoZone stores.

I can't help chiming in on this because I'm such a rebel - I use straight petroleum based 40W in my boat and have had no problems, no measurable wear, no smoke, no leaks, nothing adverse or anything that could even be considered an oil related problem. I've got 130k miles on my Whipple supercharged Chevy C1500 truck using 5W-30 petroleum based oil.

Boat oil gets changed every 25 hrs or so and the truck every 5000 miles.

I'm so glad I spent so much money on oil so that my engines will live.

Used Mobil1 for years.
Avalanche 8.1
BMW
HP500EFI
...and soon to be the Toyo Corolla when comes time for a change (new to us).

I bought my 5.7L '87 Trans Am with 86,000 miles on it; in immaculate condition. I sold it with 120,000 on it, and its entire life it was getting Wix Filters and Mobil1. Up to 86,000 miles were relatively easy, as I bought it from an older guy. 86,000 to 120,000 were not so easy, (duh, I was 19).

Mobile is good stuff ,,and their new tri formula is better ,,

40 wt straight oils for the 60's before they perfected multi weight oil ,multi starts off thiner to lube better on start up 40 wt can be thicker than the advertised 40 wt cold and its really tough on bearings again conv will work but the syn. sure gives you insurance and better all around protection as these threads have said over the last months