Hey guys,

So I've been on the hunt for a G35, found a nicely priced 04 a/t, the owner told me it consumes 1 qt @ 1000 miles. Found out this was way too much and I should stay clear. Found another 04 a/t, asked the buyer if it burned oil. He said only half a qt every 4000 miles. Guy starts suggesting I add in the oil catch can to fix it. I kept questioning about the oil consumption, asked if he needed to top off before oil changes he said "yes I have to put in about a quart". His math doesn't really seem to be adding up and it's a wicket deal on the g35. Should I stay clear from this dude? Anyone have any suggestions ;-;

Naturally all of these cars are around 100k, or a bit over.

 

Get a compression check done on them, it will tell you pretty much everything you need to know. If the current owner has an oil consumption PROBLEM and not just natural VQ35DE oil consumption and he is currently running a fully synthetic oil then it could be contributing to EXCESSIVE oil consumption so ask what kind of oil they use.

If the owner says they're running conventional then chances are the consumption is what it is, the catch can helps with high rpm consumption of oil vapor, the fast-moving parts in the valve cover creates a sort of oil mist that gets ingested through the PCV valve, if the engine is kept at a low rpm and driven around mildly then chances are there is an almost negligible amount of vapor being ingested and the catch can would do nothing.

Downshifting to slow the vehicle contributes to excessive oil consumption because of the high vacuum condition, 5AT equipped vehicles this is a non-issue but the 6MT it's very real. Running the motor hard before it's up to temp (thermal expansion) will contribute to OC as well.

Basically what I'm saying is driver habits can contribute to oil consumption just as much as worn mechanical components, the compression check eliminates (or at least measures) mechanical failure as the point of consumption and is a fairly accurate way to measure the expected life of the motor. The FSM states 185psi for an engine in good health, if you WOT while doing the check expect numbers to be higher than if you don't have someone stepping on the throttle.

Personally I like a hot AND cold check of compression but just a run-of-the-mill hot check is probably all you need.

EDIT: I've easily consumed 1 qt over 1k miles running the **** out of my '06 rev-up but when driving normally it falls into an acceptable level of OC, non-rev versions of the engine don't have the POTENTIAL for as much natural OC due to the decreased redline but most of them drink oil to some degree...

 

Very insightful.

the seller did mention he's using synthetic, this is not causing permanent damage, correct? It's just causing the oil to burn faster?

 

I've been using synthetic oil in Slick since her 1K mile birthday and changing it every 3K miles since! I can guarantee if she was torn down there would be zero sludge and absolutely no build up anywhere...and she has no OC issues at 72K miles! OC isn't caused by synthetic oil but poor quality rings where Nissan tried to save a dime!
Gary

 

OC isn't CAUSED BY synthetic no, but if an engine has worn rings then using synthetic can INCREASE consumption.

The molecules are smaller and slip past worn rings easier.

 

I'm not planning on dropping the cash to rebuild, is this a.car I should stay away from?

 

Only you can make that decision Take it in to Nissan for a pre-purchase inspection and have them look over it, have them do the compression test, etc. Then you can make an informed decision rather than relying on words that came from the previous owners face. It's worth the $150.

 

I respect your maintenance on your car, but why are you changing sysnthetic every 3k? That's about half the life of a synthetic oil