Whats wrong with my M?

[cji4130]

hey guys,

i sense i have a pricey issue brewing. hopefully i just measured wrong, but on my last oil change(9/27/12) after only 2700 miles i only drained about 2.5 quarts of oil!! i even dumped what was left in the filter for good measure. i used 5w-30 full synthetic for awhile, and switched to 10w-30 full synthetic, thinking a heavier oil was needed. made no difference. also on this last change, i replaced the oil cooler o-ring, hoping that might help somewhat with this consumption issue. ill let you know next oil change if it has improved. At 89,700, im not getting any strange noises, CEL's of any kind. the car runs excellent, however i noticed sometimes i get a rotten egg smell. i never check my fuel economy but did today, do these numbers look right to you?? 9MPG!?! wtf?


i upgraded my exhaust last month as well, installing a new y pipe, mid pipe, and mufflers.

[antzrus]

The mileage seems low. I get about 10-12 miles in city, 22-24 on the highway, but I'm easy on the peddle. The rotten egg smell is something I've noted at times too. Your oil consumption is crazy! You must be smoking a lot! I go through about a quart and 1/2 after 12K (my change interval) w/Mobil 1 10w-30. I've got 75k on her. Runs like a champ!!

[wingFeather]

I have not experienced anything like this with either of my M's. Rotten egg smell is NOT normal. This advice is not from my own experience, but from advice I've heard, so take it with a grain of salt:

"Do you usually fill up at the same gas station? They could be getting bad gas, which burns poorly - or worse, has damaged the emissions system causing the engine to run rich (low MPG & burned up your catalytic converters)."

[trayday]

what wing feather said. the rotten egg smell is most likely your cats and need replaced.

[cji4130]

The mileage seems low. I get about 10-12 miles in city, 22-24 on the highway, but I'm easy on the peddle. The rotten egg smell is something I've noted at times too. Your oil consumption is crazy! You must be smoking a lot! I go through about a quart and 1/2 after 12K (my change interval) w/Mobil 1 10w-30. I've got 75k on her. Runs like a champ!!

theres never any smoke of any kind coming from my exhaust!

I have not experienced anything like this with either of my M's. Rotten egg smell is NOT normal. This advice is not from my own experience, but from advice I've heard, so take it with a grain of salt:

"Do you usually fill up at the same gas station? They could be getting bad gas, which burns poorly - or worse, has damaged the emissions system causing the engine to run rich (low MPG & burned up your catalytic converters)."

i usually fill up with premium shell once or twice a month and sunoco regular in between. im not a very spirited driver, even my girlfriend says i drive way to slow lol. is there anything i can do? i would like to get a couple more years out of the car. i dont see how replacing the cats would make a difference.

[wingFeather]

Sorry to ask so many questions, but diagnosing a problem requires them...

When was the last time you replaced the spark plugs? Engine air filter? Those can also cause poor fuel burn & consumption.

The cats could be ruined from poorly burning fuel, but I would start with the items above as they are cheaper.

Lastly, give your car an "Italian tune-up" every week. Run the snot out of it. Floor that gas peddle! Many engines cannot handle being babied & must be put through some hot laps regularly to burn off the carbon build up over time.

Good luck!

[cji4130]

Sorry to ask so many questions, but diagnosing a problem requires them...

When was the last time you replaced the spark plugs? Engine air filter? Those can also cause poor fuel burn & consumption.

The cats could be ruined from poorly burning fuel, but I would start with the items above as they are cheaper.

Lastly, give your car an "Italian tune-up" every week. Run the snot out of it. Floor that gas peddle! Many engines cannot handle being babied & must be put through some hot laps regularly to burn off the carbon build up over time.

Good luck!

no please ask as many questions as possible! lol that's how we figure out what the issue is, and is not! the spark plugs have never been replaced as far as i know. i was made aware that it is unnecessary until the 100K mile mark and was hoping i could hold out until then. the engine air filter was replaced about 8 months ago and was inspected when i did the last oil change, i used the air gun to clean some of the larger pollen spores, moths, an other small debris. the filter still looks clean, and brand new. as for the cats, i will not be replacing those any time soon. if anything was wrong with them, wouldn't i be seeing a CEL? i suppose ill try to be a little harder on her, but im soo worried that might make the issue worse! i love my M the last thing i want to do is blow the engine

[cji4130]

The mileage seems low. I get about 10-12 miles in city, 22-24 on the highway, but I'm easy on the peddle. The rotten egg smell is something I've noted at times too. Your oil consumption is crazy! You must be smoking a lot! I go through about a quart and 1/2 after 12K (my change interval) w/Mobil 1 10w-30. I've got 75k on her. Runs like a champ!!

Are you running Full Synthetic?

[wingFeather]

Are you running Full Synthetic?

Yes he is. Do you think that is the problem? Maybe it's too thin & getting past the rings?

My current M was run on dino oil its whole life (far as I know). Even with this, it still burned a considerable amount between changes. I noticed that the previous owner was changing at 7-10K intervals. Since I bought it, I've been using Castrol dino oil with 3K changes. I've noticed consumption go down, probably because the carbon build up has been reduced thanks to the replenishing of detergents every 3K in the fresh oil.

I suggest the spark plugs because if your disappearing oil has been getting into the chamber, then they may be coated with junk (or burned) & not being the most efficient. This can in turn decrease the life of coil packs, and the cats, so it is not a waste if you replace them "10k miles early"... it is actually cheap insurance : )

But I'm sort of taking shots in the dark here. Like I said, never experienced this issue... just going on my general car maint experience.

[antzrus]

I'm really sorry to hear about your cats. I used to take my cat for rides in the M, but then she would puke all over my genuine coco mats. I don't take her for rides anymore.

She died.

[trayday]

I would say your cats and that is why the poor fuel consumption and smell of rotten eggs. with the car running go back to your exhaust tips and smell for rotten eggs. Then I would get under neath and tap on the cats with a rubber mallet and listen for loose and broken parts. If plugs were bad it would probably have your engine shaking violently.

As for your CEL I have a worn cat from my car being lowered on the OEM rims and my CEL isnt on. I have also had to replace an injector on my 2nd engine that I'm on with 10k and no CEL lit up.

[wingFeather]

she would puke all over my genuine coco mats.

High flow cats I presume?

[CPJ LB]

hey guys,

i sense i have a pricey issue brewing. hopefully i just measured wrong, but on my last oil change(9/27/12) after only 2700 miles i only drained about 2.5 quarts of oil!! i even dumped what was left in the filter for good measure. i used 5w-30 full synthetic for awhile, and switched to 10w-30 full synthetic, thinking a heavier oil was needed. made no difference. also on this last change, i replaced the oil cooler o-ring, hoping that might help somewhat with this consumption issue. ill let you know next oil change if it has improved. At 89,700, im not getting any strange noises, CEL's of any kind. the car runs excellent, however i noticed sometimes i get a rotten egg smell. i never check my fuel economy but did today, do these numbers look right to you?? 9MPG!?! wtf?

i upgraded my exhaust last month as well, installing a new y pipe, mid pipe, and mufflers.

where do you live? east coast, west coast??? 5w/30 is fine...here's a few things to check for and you can do it yourself:

PCV valve (easy to remove and replace -- takes less than 10mins) -- important maintenance...

spark plugs (change out and also check for any leaks within the spark plug well -- bad valve cover gasket rings keeping oil out of the spark plug well and coil pak)

Cats (rotten egg smell -- like others have mentioned)

Air filter (when has it been changed or cleaned out)

your mileage is up there, so now's the time to do the maintenance...good luck and let us know

[The00Dustin]

I thought the first thing to check for rotten egg smell was the battery (sulfur smells like rotten eggs, a bad battery releases sulfur, the batter yis right in front of the cabin air intake). I would say go take the cover off of the battery when you smell that just to eliminate it. Beyond that, if you think you have an oil issue, check your level regularly and fill it when it's a quart low. That's how you keep from blowing up the engine until you find the cause (which you still do need to find). Regarding the fuel economy, and the oil level for that matter, you don't say how long you've owned the car or how many miles you've put on it, so you haven't given us any kind of "normal for you" to compare these numbers to. For all I know, you bought the car with 3 quarts of oil in it and drove 2700 miles, then found that fuel economy chart, which the previous owner accidentally reset multiple times in a row, leading to the blank bars, and perhaps the previous owner drove only in town, and not so gently (or raced) to get the average you are seeing on the computer. That having been said, in addition to watching the oil level, calculate the fuel economy manually for a few tanks and see how the computer stacks up (or if you are disciplined enough, always keep a separate manual record so if the computer ever goes crazy you know sooner).

[atlM35]

Get a compression test, you might have cracked piston ring(s).
That could be the cause of your excessive oil consumption, clogging the cats to cause the smell and fuel mileage... but that's just my guess. I would start with a compression test to get an idea of the internal health of your motor.

If you have any oil on the ground, check valve cover gasket for leaks or any other seals.
Check PCV system.

[cji4130]

hey guys,

i sense i have a pricey issue brewing. hopefully i just measured wrong, but on my last oil change(9/27/12) after only 2700 miles i only drained about 2.5 quarts of oil!! i even dumped what was left in the filter for good measure. i used 5w-30 full synthetic for awhile, and switched to 10w-30 full synthetic, thinking a heavier oil was needed. made no difference. also on this last change, i replaced the oil cooler o-ring, hoping that might help somewhat with this consumption issue. ill let you know next oil change if it has improved. At 89,700, im not getting any strange noises, CEL's of any kind. the car runs excellent, however i noticed sometimes i get a rotten egg smell. i never check my fuel economy but did today, do these numbers look right to you?? 9MPG!?! wtf?

i upgraded my exhaust last month as well, installing a new y pipe, mid pipe, and mufflers.

where do you live? east coast, west coast??? 5w/30 is fine...here's a few things to check for and you can do it yourself:

PCV valve (easy to remove and replace -- takes less than 10mins) -- important maintenance...

spark plugs (change out and also check for any leaks within the spark plug well -- bad valve cover gasket rings keeping oil out of the spark plug well and coil pak)

Cats (rotten egg smell -- like others have mentioned)

Air filter (when has it been changed or cleaned out)

your mileage is up there, so now's the time to do the maintenance...good luck and let us know

I live in new york city. i have heard about replacing the pcv valve, but could not find a how-to on it. im somewhat mechanically inclined and have done most of the basic maintenance myself(front and rear differential fluid, Both drive belts and pulley, oil and filter, oil cooler seal, engine air filter, cabin air filter, power steering fluid, pads and rotors, etc..) so any help with that would be appreciated.

[wingFeather]

compression test

Good point! A compression test could tell if there is a more serious mechanical problem. The test is cheap if you buy your own gauge set from Harbor Freight!

[myother45isalesbaer]

Many good posts. I totally agree with getting a compression check. It is the only way you can determine the internal condition of the engine. As for the sulfer smell, that is a by-product of making gasoline which they take out of gasoline. Maybe you got a bad tank full. As for oil consumption I am the odd man out on this issue. My old 2004 ate syn oil like it was going out of style. I went back to dino oil and oil consumption went down to half a quart every 3k miles.

First thing I would do is get a compression check and see whats going on inside the motor.

[cji4130]

Many good posts. I totally agree with getting a compression check. It is the only way you can determine the internal condition of the engine. As for the sulfer smell, that is a by-product of making gasoline which they take out of gasoline. Maybe you got a bad tank full. As for oil consumption I am the odd man out on this issue. My old 2004 ate syn oil like it was going out of style. I went back to dino oil and oil consumption went down to half a quart every 3k miles.

First thing I would do is get a compression check and see whats going on inside the motor.

well since giving my car the "italian tune-up" my MPG's have gone from 8.9 to 10.5 which i see as a definite improvement. as for the compression test, i dont know if ill be able to do that myself (sounds somewhat difficult). would you recommend switching to a non-synthetic oil next change? is that what is meant by "dino" oil? what are the major benefits of full synthetic oil? my father gets mad when i dont put full synthetic oil in my cars lol whats his problem? also can someone give some info on changing the pcv valve on our M's

[myother45isalesbaer]

Not sure what an Italian Tune up is. I still highly recommend a compression check even if it costs some bucks to have it done. Its the gold standard of find out what is going on inside the motor. Personally I would not proceed with any repairs until you get the compression check done. Dino oil is any non-synthetic oil. Like I said, my car is a fluke. It consumes less oil on non-synthetic oil.

Get the compression check done by a good mechanic. Its worth the bucks for peace of mind and to determine if there is an internal engine problem.

[atlM35]

Italian tune-up job is just driving full throttle for a while in hope of blowing out carbon deposits and anything else that might be built up.
I perform this on a daily basis

[cruzad3r]

here's what i do with my car and if you think it might help, you're more than welcome to try

1- replace the air filter. this part is cheap and should replace around 10-12k miles. 15k if you want to push it but nothing higher. dirty air is going to hurt mpg
2- run a bottle of Chevron Techron Concentrate Plus Fuel System Cleaner and you can get these at any auto part store (advance auto, autozone, etc)
3- repeat step 2 when you fill up again. i usually run these once a month but in your case, twice will not hurt anything.
4- try this bosch oil filter instead of what you're currently using High-Performance Oil Filter by Bosch Distance Plus (part#D3500) - you can get these at any auto part store even online
5- oil brand and type is totally up to you but you should check your oil level every 1k mile to see the rate of consumption.

other than that, you can do a full tune up, new plugs, engine cover valve and pcv valve. all of these are illustrated in the manual that you can download here. it will take some time for you to read and make sense but it's there. compression testing and faulty cat are out of my realm as i haven't done it so i'm not going to offer any advice there.

good luck and remember, whatever you do, do not do everything at once because then you don't know what's the culprit.

[myother45isalesbaer]

Still very good advice from many posters. What I don't get is your car is a 6 cylinder and mine is an 8. I get 14-18 city driving depending on how many times I give it full pedal. At steady speed on the highway I get 19-24mpg again dependent on how many times I smack the snot out of the car. Given the fact my engine is larger in cubic inches my mileage should be lower than yours. I still highly recommend a compression check to see if there is a cylinder with internal issues before you proceed further in replacing parts. Your MPG seems way too low to me and just throwing money into various items in my OP is not the way to go until you get the compression check.

[bmiller79]

Agree with Myother45... I have an M35x and I think its bad when I get down to 16 mpg for city driving. On the highway I usually get about 22 mpg. Something else must be wrong.

On a separate but related note, my exhaust also emits the rotten egg smell. I have 151,000 miles though, and likely need new cats.

[EniGmA1987]

i usually fill up with premium shell once or twice a month and sunoco regular in between

Many people (including myself) have had very bad results from Shell gas in our engines. And not just the M, I know people with G's and Nissan cars who have said the same.

[cji4130]

this issue was caused by a a massive crack in my intake tube..replaced and mpg is now around 12 =)

[TXT]

You meant 21 mpg correct?

[cji4130]

You meant 21 mpg correct?

i live in new york city, so. no. i meant 12 lol

[TDot]

i live in new york city, so. no. i meant 12 lol

Lol +1

[finikM35]

haha +1 for NYC i average 13.8