Eggplant Cab

I just had a 94 C2 Cab put through a tune. Valves were adjusted, sparks changed and distributor caps and wires too. Oxygen sensor and fuel filters all changed as well. The car is running super smooth and there are no leaks but now the car is consuming oil at a higher level than before. Before I had 2000miles per quart. Now I'm getting about 800miles/quart (extrapolated from a 400mile drive which consumed 1/2 quart). Can a tune up screw up oil consumption that badly? There are definitely no leaks but this consumption increase is a bit worrying. I also switched from Mobil 1 0W40 to 5W-50. I'm also wondering if mixing the 2 grades (since I'm out of 5W50 after this next top up.) is ok.

Christer

Hi

Unless you can see smoke then I think this must be a 'measurement error'() because thats quite a change. I would monitor for the next 2000 miles to get a better average.....and don't worry in the meantime!

Indycam

Hiya Eggplant Cab
Other than the oil , nothing on that list should affect oil use . The weight being changed up , would normally reduce consumption . The statement that the " car is running super smooth " tells me that the job was done well , I guess . Mixing oils from the same manufacturer and type , should be ok .
Mobil 1 0W40 & 5W-50 together should be fine . But if you can get some 5-50 that would be better .

Eggplant Cab

Thanks guys. I'll check it out again. I've also noticed an increase in gas consumption too, but I attribute that to the thicker 5W-50 oil. It usually does 25-26 mpg on the highway at 70+mph. Dropped to 23 mpg for the drive out yesterday. I knew oil weights could affect gas consumption maybe 2-3% but a 10% drop is surprising.
I can't get anymore of the 5W-50. I brought it back from Europe just to try. Can't find anyone in the US who carries it. I would think it would be the perfect oil for US, esp those in the southern regions where temp ranges are more varied and high temps in the summer.
There's no smoke except for the morning misty burnout. I think it may be burning a bit of fuel so I'll bring it back in to check. It may be running too rich.

Indycam

The gas consumption is funny , a tune up should get you beter fuel consumption .
The oil can be shipped in .

Indycam

"5W-50 fully synthetic was a simple blend of PAO (Polyalphaolefin ) synthetic and complementary additives. In its time it was the best oil on the market. However, our main client base technically demanded advancement in our offer. Mobil continually develop products and we have now engineered a formulation of different synthetic base oils further enhance our product.

Areas of concern were fuel economy, product durability and emissions. We use two types of the PAO and an ester as used in jet engine lubrication. This results in a product that is more stable at high temperatures, so it lasts longer and this has enabled us to lower the viscosity to 0W40.

0W40 is fully miscible with the older 5W-50 but the higher viscosity would not benefit you for fuel economy. However I doubt weather this is a burning issue to you with this type of vehicle! The 0W-40 will get around the engine quickly on startup so there is an advantage here and it gives improved antiwear performance so yes there is an advantage in using the new formulation. Maybe you use the 5W-50 for topup as this will have very little effect on the main charge during the service interval. "

ltbrkm3

Having come from BMW land, I'm using the oil BMW sells for their M cars. It is Castrol TWS or RS60. It is a 10w60 weight racing oil and a little pricy, but my M car loved it! It should provide great protection from the summer heat and the many track days the car will see.
Scott

Red rooster

Eggplant,
Oil + gas consumption increased does sound like the motor could be running rich. How about checking that Oxygen sensor is connected ? or working !
Just my $0.02

Geoff

Eggplant Cab

Just replaced it so it could be that. I'll check it too. Thanks

Eggplant Cab

Indy
Where did you get this info from? Mobil?
Thanks.

Indycam

Hiya Eggpla
Indirectly from Mobil . I grabed it from a web site when I was searching around for 5-50 for sale .
I don't know if its up to date info . When I read it I wondered .

C H

Not sure about the 964 DME, but other computer controlled cars need to "relearn" after they have been disconnected. The garage my have disconnected the battery during service. This could account for the decrease in MPG and should improve after several days. Oil consumption? Probably was a little low after the oil change making you think there is a consumption issue.

Eggplant Cab

My mech didn't reset the DME (maybe he should've) And I personally checked the oil level after picking up the car and topped up before the big drive. I'm going for another long drive to see if there's any change. Thanks for the input.

iangray100

If you have had the O2 sensor changed you will need a "hammer" to do a full adaptation of the DME. Disconnecting the batter or driving doesn't do the job. Been there done it and brought a hammer to do the job correctly. Get you mechanic to do a rest via a hammer . thanks

Eggplant Cab

Thanks. We found that the O2 sensor wasn't working. I'll do a reset on the DME after replacing it. Maybe I should get idle stabilization as well.