Q: I just took my 2012 Audi A3 TDI for an oil and filter change at a nearby service station. The employees told me they use standard Mobil 1 oil and that this oil is fully compatible with my Audi/VW diesel engine. It was only after the fact that I thought to take a look at the Mobil 1 website, where it is indicated that Mobil 1 standard is not the recommended type of oil for my vehicle. What I've been unable to determine so far is whether "not recommended" means not ideal but will do the job — or does it mean, don't wait another day and go get the expensive synthetic oil replaced? The car is no longer under warranty. Later this year it will be sold back to Audi/VW under the buyback program. Thoughts?
— B.J., Philadelphia
A: "Audi is very particular about the type of oil that can be used in their vehicles, especially since this is a diesel. The regular Mobil 1 does not have a current diesel API rating and would not interact well with the Diesel Particulate Filter. This vehicle needs to be using the Mobil 1 ESP 5W-30, which is specially formulated to protect both the engine and the emissions system. I would replace the oil as soon as possible. If anything happens to the engine, we cannot warranty the oil," according to Jake Ackerman of ExxonMobil. Audi spokesperson Amelia Fine-Morrison said that "the vehicle in question … needs a low-ash synthetic, and therefore the Mobil 1 standard is not recommended. The shop should be held responsible for this error, and we recommend that the customer request that it is replaced with an approved product. While the replacement does not need to happen today, it should be replaced soon. For reference on approved oils, 504/507 oils are what are needed for the TDI engines, as stated in the owner's manual."
Q: I have a 2008 Hyundai Elantra. I have noticed that when I use my TomTom GPS at highway speeds, the mph reading on the GPS is usually 4 mph less than what is shown on my speedometer. In your opinion is the GPS actually more accurate than the speedometer?
— F.S., Millville, N.J.
A: Geopositioning satellites orbit about 12,550 miles above the earth. Although there are algorithms to correct for delay, your TomTom may not be as accurate as your vehicle speedometer. It is easy to check your speedo. Have a friend clock you with a stopwatch while you maintain exactly 60 mph over one mile, or better yet, over five miles. If it does not jibe at 60 seconds per mile, your speedo is off. Of course an alternative is to speed past a trooper and see if his radar reading is the same as your speedometer reading. This is usually a more expensive option, though.
Q: The instrument cluster on our 2004 Buick LeSabre has been acting strange lately. The rpm gauge is always at zero and the speed gauge acts erroneous at times. The gauge indicated speeds as high as 140 mph when driving very slowly. Is there an easy fix for this problem?
— D.C., Camillus, N.Y.
A: Instrument panel clusters are self-contained units. The entire cluster must be replaced. There are numerous companies repairing and rebuilding clusters. You can search for them on the internet. One shop we have used to replace the cluster on Mrs. Motormouth's car is Southern Electric (www.instrumentclusters.com, 888-363-1599).
Send questions along with name and town to Motormouth, Rides, Chicago Tribune, 435 N. Michigan Ave., Fourth Floor, Chicago, IL 60611 or firstname.lastname@example.org.