Help please - oil consumption and smoking M35

[davidfromdallas]

First post here, but have consumed much great information including topics on other smoking M35s. Any and all replies and help would be greatly appreciated.

The car info:
-- 2006 M35 Sport, 112,000 miles
-- Mobile 1 5w-30, changed every 5K - 8K as suggested by Blackstone Labs who does my oil analysis at every oil change
-- Latest oil analysis shows no indication of engine wear (metals, etc.) in the oil, in fact no abnormalities at all when compared to prior samples
-- Spark Plugs changed at 108,000
-- Air filter changed at 108,000
-- At spark plug change noticed a small amount of oil leaking into the spark plug tube on the #6 (I think) cylinder (driver's side closest to the firewall) - this is (I think) the valve cover leak I have read about here.

My symptoms:
(1) Oil consumption is up;
-- previous to 90K miles I would change every 5K-8K miles) and not have to add a drop of oil
-- Now I am adding 1/2 qt. every 1,000 miles or so; this seemed to start happening quite suddenly (everything fine on one oil change; next oil change - wow, not much oil there).
(2) Gas mileage is down
-- was WAY down until spark plug change
-- seems to have improved - now at 18.1 for mostly city and 18.5 for city/hwy combined; this is about 1 mpg less than the normal average for the car
(3) Now the problem
-- when cruising at 70 mph on the highway, then putting my foot in it to accelerate the car tends to blow a lot of blue smoke under full throttle - enough that it is embarrassing and looks like a mosquito-fogger. This is a 70 to 85-90 acceleration run.
-- When accelerating from a stoplight at full throttle to about 50 mph there is no smoke even though I rev to redline
-- When running steady throttle or light acceleration there is no smoke
-- There is no smoke at startup

So the question is "where should I start the investigation"? From the posts on this forum it seems like there are some possible culprits:
-- Valve cover leak; but wouldn't that cause smoke all the time not just on highway full-throttle runs?
-- PCV valve - clean / replace
-- Rings - do a compression test; but wouldn't it smoke all the time if this was the problem?
-- Some other dreaded disease I haven't seen or thought of yet...

Like I said - any help would be greatly appreciated...
DJ

[CPJ LB]

welcome!!! I'd start by changing the valve covers and gaskets...the spark plug seals have gone bad and if you have oil in the spark plug tubes, that will reck your gas mileage and efficiency. your car is probably 'laboring' to keep consistent power because the spark plug coil is probably covered in oil as well....so you're technically trying to get max power from 5 out of the 6 cylinders....

also, you may want to start using a 'high mileage' oil to help with seals...I know Mobil 1 has a 'high mileage' choice. it might be a possibility that the 'slippery' synthetic oil is passing through gaps within the seals of a high mileage car.

These engines will run strong even at high mileage, but just need to get the maintenance done. I also have an 06 M35 sport and I'm currently at 143K miles...still going strong.

as far as the blue smoke, I don't remember what that indicates, but I think different color smoke is going to be symptoms of various issues...(black, blue, white smoke...)

[M35Squirrel]

Your own diagnosis is pretty good already.

I would start with opening up the plenum clam shell and see how much oil is in there. Then I would replace the valve cover gaskets and spark plug seals. The PCV is easy to change once you have the plenum off, and it's cheap so change it. If the plenum is off, check the plugs again and see if there is oil deposit.

Seafoam it probably won't hurt. But if all else fails and the rings or valve seals are likely the culprit, put a can of engine restorer, because you have nothing else to lose at this point.

And I hope you weren't in the Houston area before July 2nd:
http://www.houstonchronicle.com/busines ... 613765.php

[davidfromdallas]

M35Squirrel and CPJ-LB - thank you for the replies, information, and encouraging words. I am traveling for the next six weeks (not via the M35) so I will not be able to try anything until mid-September, but I will report back after the steps as M35Squirrel suggested. I'm sure I can find directions for all of that on the forum.

Again, many thanks!

[davidfromdallas]

Just a wrap-up on this topic.
I did have the valve covers changed (both of them, even though only the driver's side spark plug seals were leaking).

Ultimately the leak was so bad that oil was spilling into the exhaust system ans causing the blue smoke under hard acceleration.

The result:
-- Gas mileage went from 18.1 to 19.5
-- No more oil consumption
-- No more blue smoke

Price was a little high (valve covers were $300 each from dealer - only place you can get them).
Total bill was $1,400 (independent repair shop), but I had a bunch of other work done:
-- Flush and replace brake fluid
-- Replace differential oil
-- Both belts replaced
-- Fix suspension rattle front left (bushing)

[CPJ LB]

Just a wrap-up on this topic.
I did have the valve covers changed (both of them, even though only the driver's side spark plug seals were leaking).

Ultimately the leak was so bad that oil was spilling into the exhaust system ans causing the blue smoke under hard acceleration.

The result:
-- Gas mileage went from 18.1 to 19.5
-- No more oil consumption
-- No more blue smoke

Price was a little high (valve covers were $300 each from dealer - only place you can get them).
Total bill was $1,400 (independent repair shop), but I had a bunch of other work done:
-- Flush and replace brake fluid
-- Replace differential oil
-- Both belts replaced
-- Fix suspension rattle front left (bushing)

good to hear that you got your issue fixed
Enjoy the M for many more miles!!!

[M35Squirrel]

Price was a little high (valve covers were $300 each from dealer - only place you can get them).

wait, what? is that a 3 and two 0's after? unbelievable...... wait, that price is each...? alright they better come with Nismo logos on them!

[CPJ LB]

^the price for those parts is just tooooo much. Nissan is making a killing since they built the spark plug gaskets within the valve covers.... The best price that I found was at OC Infiniti (in Southern California). Since I live close by, I shop on their online store, get the price, and then drive down and pick up the part. Their retail prices are just huge mark-ups....

Example:

Air Filter
Retail price = over $22

Online price = $16