Synthetic Oil

I have a pair 454 EFI engines

I have a pair 454 EFI engines with 850 hrs.Is it OK to switch to synthetic oil? Please give Pro and Cons

Art Dunn

"Art, Synthetic oil is recomme

"Art, Synthetic oil is recommended for those motors, however, it is not automotive synthetic oil. Mercruiser recommends their multiweight synthetic oil, which is quite different. Pros are hard to identify. Cons are higher cost. BTW, these are the same pros and cons as the automotive world."

"Have these always had synthet

"Have these always had synthetics or petroleum based oil?

1) expense relative to the benefit. With 850 hours, these engines are well worn.
2) switching to synthetic late in life may free up gunk and soften seals resulting in leaks you didnt have before."

"Even with synthetic oils, the

"Even with synthetic oils, the filter is still the question. Synthetic may last longer without breaking down, but the filter still needs to be changed on a regular basis. Tim"

"After several conversations w

"After several conversations with mercruiser and another unamed drive system manufacturer on oils they have stated that the expence of synthetic oil is not really worth it due to the fact that in a marine environment the oil will get contaminated and must be changed at the required intervals (100 hours or 120 days) anyway. Use a good pet based oil and you will be fine. Remember that you should not go down in viscosity. I.E. from a 10w40 to 10w30. Some of my customers require that I use the merc branded oil, which is fine oil also. The choice is up to you."

"Boatrep1, I have heard of fo

"Boatrep1, I have heard of folks using conventional Automobile multivis (10W-40)oil in their sterndrive engines. I know that Mercruiser does not recommend it, but does recommend a straight weight (ie SAE 30) automotive oil. I am concerned that you appear to be in the business of maintaining boats. What makes you think that a automotive multivis oil is adequate for a sterndrive engine, when Mercruiser doesn't?"

According to the Mercruiser en

According to the Mercruiser engineer that I spoke to there is no difference in automotive or marine engine crankcase lubrication oil as long as it meets the SAE spec recommended for the engine. After having been through 30 years of Mercruiser manuals (issued by Mercruiser) many different types of oils and wieghts have been recommened over the years and all specify an SAE spec. My example was simply to show the original poster that you should never go down in viscosity not to recommend an oil.

"I've been using Amsoil on

"I've been using Amsoil on my 5.7 Merc Inboards for the last3 seasons...no problems, or leaks...gauage stays @ 40-50 psi's eaven after running for a few hours straight, and goes down to 20 at idle....after a few minutes at idle it goes back up to 40-60..stays pretty golden thru most of the season too which is about 60-75 hrs"

"Gentalmen:

Thank you for a

"Gentalmen:

Thank you for all your advise, after reviewing all these messages. I think I will keep using a good grade of 40 SAE oil Thank you all"