What's the best oil to run in 525efi Not race but everyday oil change every 20-25 hours. Synthetic or not?

Mercury reccomends 25W-40 for the 525's and that's what I use. Philly likes snythetic and I called Merc and asked them. They have not tested snythetic so officially cannot approve of it. I also think the Merc manual says to change it every 30 hours or 30 days.

They also recommend using Mercury oil in the 525 efi.

If they had Mercury gas they would recommend it also.

I use Mobil 1 syn in everything.

I am going to have to agree with LS... conventional oil still derives from crude and contains sulfer, nitrogen, benzenes, and paraffin waxes, which all lead to early breakdown and the oil does not do a good job moving around the engine witin itself ( almost clashes with its own oil) Synthetic is all chemical made, and cannot be beat these days... But most important they all need to be changed every 30 -40 as stated. The synthtic may not break down as easy and quick and still may have alot of life left at 30 hours, but you need to remove all the engine paticles within the oil and you can only do that by changing. my .02

P.S. I wonder why LS specifically uses Mobil 1 ? oh yea he must have a few Mercedes manuals around !!

We have been a Mobil distributor for 30 years. We have always used Mobil 1 in our Merc engines. In our 525's we always used the 15w50. We always ran samples of the used oil with the Mobil "Signum" Oil Analysis.

We never had any abnormal metal wear or product breakdown.

I wouldn't imagine there would be a problem with synthetics in today's engines, unless they had some sort of custom materials used for the seals (doubt it). You won't get much benefit from a synthetic in a marine engine with short change intervals. Thermal breakdown of the oil is low, because the temperatures are low with the cooler. You won't get the cold weather benefit, unless you boat in the winter in the northern latitudes. Changing it every 25 hours won't gain you any of the longevity benefits either. You might as well run a good quality non-synthetic. The best ones are from the oil companies such as Chevron and Shell. Avoid Pennzoil, Valvoline, and the other brands you find on TV and the auto parts stores. They spend most of their money on marketing, rather than research and the product.

Michael

A boat engines load is a lot tougher than a car. Esp when you are pushing higher rpm. We have destroyed synthetics after a poker run with 4 hours. In addition, if you have a hard weekend with big or little power you can toast the oil. My recommendation would go under the Q & A forum and see what the boys have to say about Lubrication. There is some good information in there.

I can also hook you up with a distributor in the St. Louis area to hopefully save you some money.

Mobile 1 synth. 15w-50 since you cant find 20w-50 anymore.

Synthetic. Definitely. Amsoil's got a synthetic lube for just about anything you can think of. They spend their money on research and development, not advertising........ they're also one of the few companies that will stand behind their 25,000 mile/1 year oil change intervals on cars.

The Mobil 1 20w50 is still available. Distributors have to by in by full pallet or layers.. I can get you in touch with a distributor in your area.

Beaumont PVL 98HC76 MOBIL 1 V-TWIN 20W-50,6X1QT.
Cicero PVL 98HC76 MOBIL 1 V-TWIN 20W-50,6X1QT.
Kansas City PVL 98HC76 MOBIL 1 V-TWIN 20W-50,6X1QT.
Paulsboro PVL 98HC76 MOBIL 1 V-TWIN 20W-50,6X1QT.
Port Allen PVL 98HC76 MOBIL 1 V-TWIN 20W-50,6X1QT.
Vernon PVL 98HC76 MOBIL 1 V-TWIN 20W-50,6X1QT.
Grane PVL 98HC76 MOBIL 1 V-TWIN 20W-50,6X1QT.