QUESTION: You have recommended changing coolant every 30,000 miles or three years. How does universal coolant compare to green, orange, etc., types of coolant?
ANSWER: As coolants and engine technology continue to improve, I’ve softened my position on coolant changes. Assuming a long-life coolant and 15,000-25,000 annual mileage, I’m willing to go five years now — a huge step for me.
There are basically two technologies for corrosion protection in engine coolants — inorganic and organic. The conventional antifreeze used for decades, which is usually green in color, utilizes silicates and/or phosphates to protect the various metals used in engines and radiators.
The so-called long-life coolants — often orange in color — introduced in the mid-1990s utilize organic compounds to provide anti-corrosion protection. The benefit is these compounds last longer, thus the extended-life concept. There are also several hybrid coolants used by several carmakers that combine both organic and inorganic compounds.
Universal coolants typically use organic compounds like long-life coolants and claim to be compatible with any coolant.
As confusing as the different coolants can be, remember three important things: You own and are responsible for the vehicle; if the cooling system contains any conventional antifreeze, change it every three years; and, finally, no coolant is permanent, or capable of lasting for the life of the vehicle.
Question: I have a 2006 Jeep Grand Cherokee SRT8. I took it to the dealer, and they said I have a No. 1 cylinder misfire. They checked the compression and leak down on all cylinders and everything was OK. Now they want to pull the cylinder head and check for carbon deposits on the valve and the valve possibly not rotating. The miss occurs while idling. Can you come up with any more possibilities?
ANSWER: There are several steps in the diagnostic process before deciding to remove the cylinder head for inspection.
First, decarbonize the induction system to remove any carbon buildups.
Next, connect the engine to an electronic engine analyzer to determine if the misfire is electrical rather than mechanical. This can show the actual voltage required to fire the spark plugs.
Comparing this information to the performance of the other cylinders might well identify an ignition problem with the spark plug, coils or harness. The 6.1-liter Hemi V-8 in this vehicle features twin plugs per cylinder and coil-on-plug ignition coils.
If the misfire is electrical, it may be possible to swap coil packs between different cylinders to see if the misfire follows the coils. A new pair of spark plugs in the misfiring cylinder might also help.
If the misfire is not electrical, try the same thing with the fuel injector from the misfiring cylinder. Does the misfire follow the injector?
If the misfire is neither electrical nor fuel-related, it may — and not having tried this on a dual-plug engine, I emphasize “may” — be possible to remove and disable the coil pack from that cylinder, disable the injector, remove one of the two spark plugs, and install a compression gauge with the Schrader valve stem removed so that the gauge will not hold pressure.
Starting the engine momentarily will show the actual running compression in that cylinder. If airflow into or out of that cylinder is restricted by carbon deposits or a valve problem, the running compression will be low.
QUESTION: Would it work to use a small turbine engine to run the generator in a hybrid? Are they not more efficient than internal combustion with many fewer moving parts and longer life?
ANSWER: You are correct in recognizing many of the advantages of a gas turbine engine, but these engines are most efficient in continuous load operation — not starting, stopping or changing speed to recharge batteries, run a generator or electric motor on a part-time or variable load basis.
Turbine engines in automobiles have been done before. Chrysler had prototypes on the road back in the early ’60s and, of course, the STP turbine car came within a few miles of winning the Indy 500 in 1967 with Parnelli Jones driving.
QUESTION: I’m the original owner of a ’92 5.0-liter Mustang with 60,000 miles on it. The car is driven maybe 200 miles a year. Immediately after start-up and all while it’s driven, there is an odor of varnish or wood alcohol all around the car and not necessarily from the tailpipes. It’s not the rotten egg smell from a catalytic converter. Should I be driving the vehicle more and putting in fresh gas more often? Are there any fuel additives I should be using? I’ve heard the term “sour gas” but I’m not sure what that is.
ANSWER: The most common automotive source of a varnish-like odor is stale gasoline. As gas ages, some of the hydrocarbon molecules oxidize, creating a lacquer or varnish-like residue. Remove the fuel filler cap and take a careful, small whiff. If you smell that bitter, sour odor, it’s the gas.
If you can’t drain and flush the tank, change the fuel filter, add Sea Foam Motor Treatment to the gas and run the tank as near empty as possible, then fill up with fresh gas — non-oxygenated if it’s available — and more Sea Foam.
Also, make sure the evaporative emissions system and charcoal canister are working properly and not leaking any fuel vapors.
QUESTION: I recently purchased a 2010 Mercedes ML 350 with a V-6 engine. The manual says it requires premium gas — 91 octane or higher. What are the consequences of using regular gas occasionally, given the 25-cent price difference?
ANSWER: All I can tell you is that I’ve never had an issue operating my BMWs and VWs that “require” premium on 89-90 mid-octane gas.
Paul Brand, author of “How to Repair Your Car,” is an automotive troubleshooter, driving instructor and former race-car driver.