Q: The other day I stopped at a Shell station and found their higher-octane gas contained nitrogen. I believe it said it was an additive. With all of the concerns about ethanol levels and what is safe for which cars caused me to wonder about nitrogen. When I was a kid my friends would add nitrous oxide to their hot rods to get extreme performance out of the engines. Blown engines weren’t uncommon. So is this a safe thing and/or even beneficial?

A: Don’t confuse nitrogen as a detergent additive and nitrous oxide, a performance enhancer. When nitrous oxide is exposed to the extreme temperature in the combustion chamber, the NO2 molecule splits into separate nitrogen and oxygen atoms. More oxygen allows more fuel to be burned, thus increasing power output of the engine.

Nitrogen has been used as a detergent in gasoline for some time. Its cleaning properties help reduce and remove carbon deposits from intake and exhaust valves. As such, there is benefit to your engine from the use of gasoline with nitrogen additives. And there’s no danger the nitrogen could contribute to a blown engine.

There has been some consumer concern that nitrogen added to gasoline could contribute to higher nitrogen oxide pollution. Remember EGR — exhaust gas recirculation — valves? By reintroducing a small percentage of exhaust gas to the incoming fuel/air mixture, combustion temperatures were lowered a bit to help reduce NO2 emissions. Oil companies tell us that nitrogen added as a detergent does not contribute to these emissions.


Q: I have been driving Camrys since 1984, and I drive them until they are dead. My current 2000 has about 220,000 miles on it. In July I had to drive my dad about 90 minutes away to see my mom. The struts were in need of replacement, and maybe a tire alignment, so my father felt my car wasn’t safe. I’ve had the struts replaced but still need an alignment. He thinks I should get a Ford Edge instead. I am not ready to give this car up yet and am thinking of possibly getting a van when I retire so I am holding off for now. Do you think my father is right? I want to get him off my back.


A: Be thankful he cares about you enough to make this suggestion. And tell him that if he’d like to purchase the new vehicle for you, you’d be extremely grateful!

But I don’t think he’s correct in feeling your current Camry is unsafe. I’m assuming that because it has survived 15 years and 220,000 miles, you’ve taken reasonable care of it and kept up with routine maintenance. If so, you are still comfortable and confident in the car and tires and brakes are in good shape, I think it is safe to continue driving the car.


Q: We have two vehicles that we drive less than 2,000 miles per year. One is a 2002 Toyota Corolla that sits idle in a cold Minnesota garage six months a year. The other is a 2005 Toyota Sienna van that sits in a hot Arizona garage for the other six months a year. I use 5-30 standard oil in both vehicles. If the oil looks clean, is there a need to change the oil in these vehicles more than once per year?


A: No, I don’t think so. Whether or not the oil looks relatively clean doesn’t really mean much. Remember, motor oil is the engine’s detergent so some discoloration as miles accumulate is completely normal. With so few miles driven annually in each car, the oil’s additive package has not been depleted, meaning the oil is still fully serviceable.

Once-per-year oil/filter changes on my low-annual-mileage vehicles has been my practice for many years.