Is 20w50 as good as 25w40?

[mcu]

I have an 1988 Mercruiser 350 and being in Canada, I am having an extremely<br />hard time finding 25w40. I purchased Castrol 20w50 and was ready to change<br />the oils today, but thought I'd make sure first. Is it just as good? Will it<br />cause any problems for me or my boat in the long run?<br /><br />The only thing I have found other than 20w50 is SAE 30 and SAE40 for diesel<br />trucks, which someone recommended I use. Is this correct? Please let me know<br />what you suggest!<br /><br />Thanks

 

[JB]

Re: Is 20w50 as good as 25w40?

Howdy, MCU. 20W50 would be better than 25W45. If your manufacturer agrees, MOBIL 1 would be even better than that. Don't use Mobil 1 unless all of your seals, etc. are compatible with synthetic lubricants.<br /><br />Red Sky....<br />JB

 

[ODDD1]

Re: Is 20w50 as good as 25w40?

MCU, LAST COUPLE TIMES I was in service school this question was brought forward....the jist of the answer is this...because of elevated oil temps a thicker base stock oil is needed...MCM recommends their 25W40 [of course] when questioned about what makes theirs better, was told is a multiblend, not a multiweight....should not use thinner than a 25 weight base stock for proper protection during summer time temperatures.....is the 20w50 good enough? maybe....a straight 30w would be better....be careful of synthetics..most have a very thin base weight...whats in my shop? MCM 25W40 by the drum...

 

[JB]

Re: Is 20w50 as good as 25w40?

I defer to ODDD1. He is the Man.<br /><br />Red Sky....<br />JB

 

[mcu]

Re: Is 20w50 as good as 25w40?

Thanks for the replies! I appreciate the time. I already did an oil change and put 20w50 today. Will it cause problems to my engine or performance? Should I change them for a third time this summer, or just change to 25w40 on the next oil change?