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Old 10-25-2013, 12:05 AM
Skyskiguy Skyskiguy is offline
TT Enthusiast
 
Join Date: May 2012
Boat: 2006 X30
Location: Utah
Posts: 242
MCX using a lot of oil

Last week we made our fall trip down to Lake Mead. I checked the oil before we left - it didn't registered on the dipstick! (2006 X30 w/MCX - 212 hours) I had to add about 1 1/2 quarts to get it in the middle of the operating range on the dipstick. Probably had about 50 hours on it for the summer at that point. I started to winterize it Tuesday night and when I drained the oil I got 3 quarts out of it plus whatever was in the filter (I use a high capacity Mobile 1 filter) - maybe 1/2 quart? So in three days at Lake Mead I burned a quart?! We were doing some cruising at 5000 - 5200 RPM's (at that lower elevation I could go above that but was careful not to - I need a higher pitch prop for Lake Mead and Lake Powell). We also did a good amount of tubing (three man, both solo and doubled up) as well as some skiing and hydrofoiling.
Well, that seemed like a lot of oil to burn in just a few days so tonight I did a compression test (engine warmed to temp, all spark plugs removed, fuel injectors disabled) with the following results:

1-165
2-172
3-150
4-162
5-145
6-158
7-160
8-167

Owners manual says minimum compression is 100 with no greater than 70% difference from high to low. At 145, my low is 84% of the high. According to the manual I'm fine. I've always heard 10% between high and low - I'm at 16%. SHOULD I BE WORRIED? Could cylinders 3 & 5 be causing my high oil consumption or were all 8 consuming it due to my high RPM loads?

Other info that may be helpful:
No noticeable smoke at start up.
No noticeable oil slick on the water when idling or oily residue on transom when removed from water.
No noticeable smoke when cruising at high speed.
Oil removed from engine was not milky.
No noticeable oil anywhere in bilge or on engine.

Any input from you mechanics out there would be much appreciated!
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