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lassy
09-10-2007, 08:51 AM
I was curious about oil change intervals when using the rotella synthetic in my 1999 X-star with the 5.7 LT1. that oil change was the first one i had to do since i got the boat last year, and i've put around 100 hours on it since the oil change.

should i just check the oil consistency on the dip stick? if it looks clean then keep running? or is 100 hours a good interval to change the oil?

any thoughts?

OhioProstar
09-10-2007, 09:05 AM
I usually try and change it once a season when I lay it up for the winter. That keeps any toxic residue trapped in the oil from sticking to the moving parts all winter. If you don't winterize the boat, I would think 50-100 hours is appropriate regardless of the oil type (synthetic or conventional).

Thrall
09-10-2007, 09:13 AM
I've been running dino Rotella in my LT-1. Just changed it for the winter this wknd, and w/ about 50hrs on it this year, it still looked pretty clean.
I'd say 100 hrs is ok, considering I use the stuff in my Duramax and run about 8k mi/200hrs between oil changes and the diesel runs hotter than the boat motor.

bigmac
09-10-2007, 09:38 AM
Relative to extended drain intervals, the supposed advantage of true synthetic oils is their shear stability due to their markedly decreased need for viscosity index improvers. The difference between group II base stock oils that have been catalytically refined and PAO-based synthetics is pretty negligible in that regard, however. Oil companies often tout the wonderfulness of extended drain intervals, but the auto companies (who are paying for the warranty claims) are not.

Synthetic oils have the same soot and byproduct accumulation as Group II base oils like Rotella T or Pennzoil Marine. THAT is the reason you can't extend drain intervals, not breakdown due to shearing of the VI polymer. Shearing stability is the reason why auto mfgrs went to 6000 mile intervals, and combustion byproduct accumulation is the reason you won't see them going any further.

Oil is very well hyped to the unsuspecting public, but there's nothing magic about synthetics, despite what we've all come to believe from watching TV, or listening to our mechanics who are no better educated on the subject than the rest of us.

No matter what oil you use, better to follow the mfgrs recommendations regarding drain intervals, in your car and in your boat. Indmar specifically states that you can use synthetics, but if you do, you still can't extend their recommended oil change frequency. 50 hours or end-of-season.

TMCNo1
09-10-2007, 09:42 AM
Owners manuals recommend oil changes every 50 hours and have as long as I can remember with just about every marine engine manufacturer. I wouldn't think synthetic would be much different. IIRC, when MC/Indmar had the Mobil1 program in the early '90's, 50 hours was still recommended, but what do they know!

BrianM
09-10-2007, 09:52 AM
I agree with BigMac and TMCno1. 50 hour change intervals. Might as well use the less expensive Dino Rotella or Penzoil Marine as well.

lassy
09-17-2007, 09:42 AM
so i went ahead and did the oil change this weekend.....i must say, never in my life have i made such a mess simply doing an oil change. hahaha.....it was ridiculous! luckily all the mess was on the ground and not inside the bilge. i was having serious problems!