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Auto Doctor: Low-octane gas OK for premium engines occasionally

Occasional usage of low-octane fuel won't cause long-term

Occasional usage of low-octane fuel won't cause long-term damage to engines, like that of the 2010 Chevy Camaro, that require higher-octane fuel. Credit: General Motors

Dear Doctor: I own a 2001 Pontiac Trans Am, a 2009 GMC Denali and a 2010 Chevy Camaro, all with V-8 engines that require 91 octane or higher. Due to Superstorm Sandy, I was only able to fill my vehicles regular gas at 87-octane rating. Will one or two tanks of regular hurt or damage these engines? Should I use an octane boost additive until I am able to get the higher octane gas? -- Joe

Dear Joe: There is no long-term damage from limited use of the lower octane fuel. However, you will notice a loss of power under hard acceleration. The engine knock sensors will feel the engine ping and retard the ignition timing. I would not spend any money on gas additives or octane boosters.

Dear Doctor: We recently bought a Toyota Camry Hybrid. We go south for three months in the winter. While we are away the hybrid Camry will be parked inside of an unheated garage for that period of time. Are there special preparations we need to take? Also, we noticed fuel mileage has dropped with the cooler months. We were averaging 44-plus mpg in warmer weather, but now mileage has dropped to 40-plus mpg. Your thoughts on additives? -- Don

Dear Don: You need to make sure the oil is clean and the tires have correct air pressure. I like to park the tires on either wood or thick padded carpet pieces to help prevent flat spots. As for any additives to increase mileage, I personally don't believe in them.

Dear Doctor: My son's 1999 Lincoln Continental has an overheating/coolant boil-over issue. My mechanic did a test to see if exhaust gases were in the coolant, if the head gasket was blown, as well as a test on the coolant fan functionality. The thermostat was also replaced. The issue subsided for a few days but has come back. Now the high temperature light goes on and the coolant boils over and escapes the coolant overflow tank, causing a low coolant condition. Is there anything else that can be checked? -- Chris

Dear Chris: You did not mention if the engine is a six-cylinder (which have head gasket failures). If so, then this is a common problem. If there is no exhaust gas in the cooling system, then you have to look at circulation from the water pump impeller and make sure the radiator is partly plugged and has plenty of flow. On some rare occasions there could be a blockage or collapse in a coolant hose.

Dear Doctor: Many cars today have timing belts that get replacements at the 60,000-to-90,000 mile interval. Other car manufacturers use timing chains, which do not need maintenance replacement. Why don't more automakers use timing chains? It would save consumers the expense of the timing belt changing and reduce the number of ruined of engines when the belt wears/breaks prematurely. If the timing belt is a better performance option for the engine, can't they devise easier access to it when replacement is needed? -- Rob

Dear Rob: The use of timing belts is due to limited space under the hood and design of the engine. Timing belts need replacement at different mileage intervals by manufacturers. This needs to be done to avoid major problems if the timing belt fails, which may lead to major internal engine damage. There are no performance gains from timing belt vs. the timing chain.

Dear Doctor: I commute just under 100 miles a day, with 90 percent of it being highway driving. I prefer a manual vs. automatic transmission. Being a GM guy, my personal car is a 2011 Corvette ZR1, but I have looked into the Chevrolet Spark. It looks like decent transportation for $15,000. What are your thoughts on the 2013 Spark? -- David

Dear David: The 2013 Spark I drove for one week was finished in a bold green that GM calls Jalapeno. Our test car had the "2LT" package, which included heated front seats, power windows and locks, steering hub controls, navigation, etc. My commute is just under an hour and 75 percent highway. I found the Spark to have ample power with its 1.2-liter 4-cylinder mated to the 5-speed manual. The fit and finish was good, seating for four was ample and there were no blind spots. The electric power steering gave good feedback and for a small car it was forgiving over rough pavement. Take one for a road-test and see if the Spark is for you.

Dear Doctor: I am a 76-year-old woman and rely on others to keep my 1992 Cadillac Sedan DeVille in good repair and safe on the road. When I have to wait inside the car for lengths of time should it be left running for any length of time or should the engine be shut off and restarted? -- Corrine

Dear Corrine: With the weather being cold it is best to leave the engine running vs. shutting it off and on. If the temperature were 90-plus degrees then shutting the engine off would be a good idea. -- Junior Damato, Motor Matters

Junior Damato is an ASE-certified Master Technician. Email questions to

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