Can cars use different octane gas at different elevations?
Q: We live in the suburbs of Chicago and drive a
2 0 1 5 Dodge Caravan, for which it’s recommended to use regular gas rated at 8 7 octane level. We just completed a road trip to Seattle and the gas stations in the Western states showed the regular gas with an octane rating of
8 5 . Do cars at higher elevations run just fine on the 8 5 regular octane rating? Could I have saved money by purchasing regular gas instead of midgrade?
— M.V., Darien, Illinois
A: At higher altitudes, the air is less dense. To maintain the air/fuel ratio, lower octane is acceptable. Modern cars adjust for changes in altitude and the driver never notices any difference in performance. That’s almost as cool as your phone’s clock changing with time zones. Q: Regarding your recent article about car break-ins and the possibility of the thief using the garage door opener, I would guess that most car owners have a stand-alone garage door opener hanging on the sun visor and it would be a cinch for the crook to open the garage door. My advice to anyone leaving their car in the driveway overnight would be to consider the door opener like another car key and bring it into the house overnight. — P.V., Niantic, Connecticut A: There are many garage door remotes that are no larger than today’s remote key fobs. Some can even be programmed to operate up to four systems. Openers have come a long way and gotten much smaller than the old lunkers that were the size of a deck of cards.
Q: Our 2 0 1 4 Kia Soul has only ever had conventional oil. We were informed by the dealership that they now only use synthetic oil. I read a while back that if a car is run on conventional for more than the first oil change, it is detrimental to change to synthetic. I went online to try to verify this, and lo and behold, it is apparently perfectly safe to switch, and even switch back and forth! I would really value your knowledgeable thoughts. — B.P., Las Vegas
A: That’s right. Not only can you switch back and forth, you may combine the two kinds of oil, as is the case with synthetic oil blends.
Q: I have a 2 0 0 8 Chrysler minivan. On my way home from work, I stopped to make a delivery. When I started again the engine was revving very high and only had second and reverse gears. I put on the flashers, got on the shoulder and drove home. I had it towed to the local transmission shop and they confirmed the situation and said it was in something they called “Limp Mode.” They said it was a broken shaft in the transmission and not worth fixing. When I picked it up, to my surprise it shifted as it is supposed to. I have been driving it short distances for three weeks and no problems, but I am afraid to take it on a longer trip. Any ideas what the problem may be?
— L.H., Annandale, Minnesota
A: Various engine or transmission sensors, or even a brake system sensor malfunction, may result in the limp home mode. This is to allow you to drive to a safe place, a repair shop or even home. The check engine light will usually glow as well. Sometimes there is a temporary glitch that can trigger the limp home strategy. A technician can interrogate the vehicle’s computer to track down the problem, fix it and send you on your safe and merry way.
Bob Weber is a writer and mechanic who became an ASE-certified Master Automobile Technician in 1976. He maintains this status by seeking certification every five years. Weber’s work appears in professional trade magazines and other consumer publications. Send questions along with name and town to motor mouth.tribune@gmail.com.