[Pilgrim]

I talked to my dealer about consumption problem and mentioned i was thinking of a rebuilt engine , he said " don't rebuild it " then i went to the best engine shop in town and explained the issue, he called me two days latter and told me he had made some calls and based on what he found out and my description that even though he had full ability to do rebuild he recommend keeping the level topped up as there was probably not enough damage to warrant a complete rebuild. said he would take my money and do a perfect job, but that if it was his car he wouldn't do a build on it. I have posted the amounts prior and it has not gotten any worse over last two years, that is when i noticed and started a log book, uses about same amount since i bought it six years ago. any thoughts.

Yes.

#1: The only drawbacks I see to just driving it the way it is are the question of (a) whether it will pass any emissions tests (do you have them? If not, disregard...) and (b) whether the oil will eventually damage the pre-catalytic converters (one just under each exhaust manifold) and the main catalytic converter. I did some quick web research and it appears that oil consumption will probably damage them at some point...but replacing them is still cheaper than an engine rebuild. I did find some comments opining that a cat which has been run and allowed to get good and hot can probably tolerate some oil passing through more easily than a cold cat will.

#2: Why do you say in an earlier post that "OEM parts will offend"? That makes no sense. OEM parts are normally the highest quality and the best fit for your vehicle. Very few OEM parts are even used in an engine rebuild other than gasket set, rings and bearings - which are not actually bearings, they're flat inserts with a coating on top. If you need to have the cylinders bored, aftermarket pistons and rings will be used.

Remember - until the engine actually has problems running, you can just feed it oil. You have not experienced any problems, and you say that your car's oil consumption has not changed in 2 years. That oil usage doesn't seem to have damaged the cat converters so far. I see no reason not to continue driving it until you experience an actual problem.

(Remember my earlier story about the GTO that used a quart every 50 miles? Incredible oil consumption, but it never fouled a plug or ran badly. However, I made a trip from Eastern WA to Seattle and back - 300 miles each way - and used a case of oil doing it. Every 100 miles I added two quarts, then kept driving. The whole darn car smelled of Havoline.)

Many people think cars have to be perfect to keep running. Not so. You can drive a car that has a LOT of problems and keep it running for a long time as long as you know what you're doing, pay attention, and understand what the consequences of driving it in that condition are.

 

[blackdog]

hey thanks for response, the reason i was looking for pre-cat mod is because it was most likely the left bank cat that was replaced under warranty that god sucked through my engine and started this problem. if i had the engine built i wouldn't want this to happen again. i found a shop in vancouver that has a mod. for this as they have done this for both murano's and 350z's. and the engine shop said something about the low tension piston rings playing a part in this as well. oh well mo runs good and if you blink you will miss the small puff of start-up smoke.

 

[Pilgrim]

Low tension rings can be caused by the engine getting too hot - it can compromise the temper in the rings and reduce their tension against the cylinder walls. But the engine would have to get pretty darn hot to do it.

 

[blackdog]

i was told nissan has low tension rings in these motors. similar to rings found in racing cars .

 

[Pilgrim]

i was told nissan has low tension rings in these motors. similar to rings found in racing cars .

I don't buy it. If all the Muranos had low tension rings *and* that was enough to cause oil consumption in yours, *then* it would cause oil consumption in many Muranos. That's not the case. This is a very simple "if-then" proposition, and it doesn't work. Their story doesn't make any sense, and I don't believe it for a second. If Muranos have low tension oil rings, then they are designed by the manufacturer to run that way without consuming excess amounts of oil. My 07 with 76K miles on it doesn't use any significant amount of oil between 5K oil changes, and it's stock.

Race cars are different in almost every detail from street cars, including the way the engines are set up and equipped. Oil consumption that's perfectly allowable for specific purposes in race cars would not be acceptable in cars sold to the public. Their comparison statement doesn't work for me.

 

[blackdog]

ya that's not what i am saying, just pointing out that with some scoring from pre-cat brick being sucked through the engine the low tension rings could let a little more oil pass, got this info from here , this site.


1) If your VQ is losing/burning oil, it is NOT because of the viscosity. The problem lies in the taper of the cylinder bore. All VQ engines have a tapered bore, and on some, it is excessive, to the point where the secondary rings and oil control rings are not making full contact with the cylinder walls. During heavy deceleration, or high rpm deceleration, the vacuum in the cylinder draws oil past these rings. In a situation where you are losing 1qt every 1000 miles, you can be sure to find secondary rings that show minimal signs of wear. (since they are not in contact with the walls, why would they wear?)

 

[Pilgrim]

ya that's not what i am saying, just pointing out that with some scoring from pre-cat brick being sucked through the engine the low tension rings could let a little more oil pass, got this info from here , this site.


1) If your VQ is losing/burning oil, it is NOT because of the viscosity. The problem lies in the taper of the cylinder bore. All VQ engines have a tapered bore, and on some, it is excessive, to the point where the secondary rings and oil control rings are not making full contact with the cylinder walls. During heavy deceleration, or high rpm deceleration, the vacuum in the cylinder draws oil past these rings. In a situation where you are losing 1qt every 1000 miles, you can be sure to find secondary rings that show minimal signs of wear. (since they are not in contact with the walls, why would they wear?)

I've heard that before and I don't believe it either. It's not physically possible to bore a tapered cylinder and have the piston not slap and the rings seal. Some day I may get corrected, but IMO whoever wrote that doesn't understand motors.

 

[blackdog]

yes a lot of bad info, worst is that machine shops are making up reasons not to build an engine, dealer recommends not rebuilding ........... trade in value is 5-6 k, used engines are to much of a risk, can't sell a problem mo private , too honest for that and don't want people coming back to me. tried trading at a used car lot and they wanted me to sign a declaration that there are no mechanical defects, well i can't do that as the consumption is an issue, but what if the transfer case went in a week, a component that i have no issue with ? i am over fifty and have never been in such a situation. nissan canada, well they have no knowledge of engine problems after a pre- cat goes through the engine. i know that is what caused the problem as it started six months after, but slowly (happened under warranty ) it does seem to have plateaued, but using oil at 160k is not acceptable , my toyota truck has 290k and uses nothing between changes.

 

[Pilgrim]

I suggest you try different machine shops or see an engine rebuilding firm. In the US there are a number of engine rebuilders, and some are turnkey - you drive the car in, they pull and rebuild the engine, then re-install.

I agree you're using a lot of oil, and you and I can probably agree that this is due to the failure of a poorly designed part. Having the pre-cats where they are is (IMO) a stupid design that invites exactly the problem you have encountered.

But as one of our politicians said, "you don't get too live in the world you want - you have to live in the world you have" (or words to that effect).

I'm betting that in BC you can find an engine rebuilder if you expand your search. If you can't, how about a drive to Seattle for a nice visit and rebuild?

 

[blackdog]

yes up here we say " you miss every shot you don't take " tried vancouver but the price went up to 8k and then add in travel and accommodation which was not even practical as they needed a week to do the job. i will check seattle but can't afford to add food and lodging for a week if it is that long.

 

[Pilgrim]

yes up here we say " you miss every shot you don't take " tried vancouver but the price went up to 8k and then add in travel and accommodation which was not even practical as they needed a week to do the job. i will check seattle but can't afford to add food and lodging for a week if it is that long.

Creative thinking here....

Drive down - take bus home - return via bus?

 

[blackdog]

yes that is what i was going to do with vancouver untill the price jumped 2k from local, will make some calls to us next week, internet search i did prior came up with a great shop in california, but that was going a little far, maybe if someone on the forum could help with a good shop in northwest ?