Dayton Daily News

Wheels: Ron writes, “I saw on a container of Mobil 1 extended service synthetic engine oil that it does not meet the GM-4718 standard, while other grades of Mobil 1 do. How significant is this? Exactly what is GM-4718?”

Halderman: Only oil meeting the General Motors Corp. factory specifications should be used. The General Motors Corp. specification includes maximum levels of antifriction additives, such as zinc dialkyl dithio phosphate, abbreviated ZDDP. This additive contains phosphate, which if burned in the cylinder of an engine, would then exit through and could degrade the catalytic converter.

Because there is always some oil consumed by the engine and to protect the catalytic converter, the oil specified in newer vehicles now has a limit on the amount of additives. What would I do? I would use only oil that has the “starburst” on the front of the oil container, which means that it meets the needs of the vehicle manufacturers for use in a gasoline engine. You were wise to check the label. Apparently, the oil was formulated to achieve extended life and as a result, other additives had to be included making it unsuitable for use in General Motors vehicles. I recommend that standard oil, instead of extended life oil, be used and changed regularly.

Wheels: An e-mail from Judy says, “I sure hope you can help with my problem. I have a 1990 Honda Accord LX Coupe, 5-speed transmission. It is parked on a 30 degree sloped driveway. Three weeks ago, I noticed a good size puddle of water on the driver’s side back floor and it was also slightly damp on the front floor on the driver’s side. This has happened twice in the last few weeks. My mechanic thought the window might be leaking from the rain we’ve had, but the door panels nor the seat are wet. Please help me solve this mystery.”

Halderman: The problem could be due to rust hole in the floor boards on the driver’s side in the rear wheel well area. When driving on wet streets, the rear tires would throw water into the wheel wells and if there is a split in a seam, this water would then flow to the lowest locations inside the vehicle.

The next time you have the oil changed, ask the service technician to check for the condition of the underside of the floor. A body shop can inspect and repair this concern. The rear window or the windshield could be leaking if it only happens when you park on your sloped driveway. I can’t think of anything else that would match your problem unless a window was down when it rained.

James D. Halderman is an ASE-certified master technician, a member of the Society of Automotive Engineers and the author of 12 textbooks. Submit your automotive care questions to Halderman via e-mail at jhalderman2@juno.com, or write him in care of: Wheels, Marketing Publications Department, Dayton Daily News, 45 S. Ludlow St., Dayton OH 45402.