Doug McAllister/Under the Hood:

You may have noticed it’s been hot lately! So what does this mean for your car? Generally when the weather goes extreme, either hot or cold, we see anything on your car that is marginal can fail.

Maybe a battery was fine one day and junk the next. How about all of the sudden a water pump or a gasket starts leaking. And in these temperatures, for sure you know by now if your air conditioning is functioning well or not.

Some items that I would take care of when it is this hot would be:

Ÿ Worn or old belts and radiator hoses — hoses can burst.

Ÿ Electric cooling fans and fan clutches.

Ÿ Oil leaks — oil can ignite when it’s this hot.

Ÿ Engine coolant should be clean and the right mixture — clean coolant will dissipate heat better.

Ÿ Radiator condition — loose or missing cooling fins can reduce cooling capacity.

Ÿ Transmission fluid condition — clean fluid helps dissipate heat.

Ÿ Tire condition — dry rotted or cracked tires should be replaced, they can come apart on long hot drives.

Ÿ Battery — as mentioned above a marginal battery can fail without notice.

Remember, don’t ignore any warning lights that may come on and as always a well-maintained car won’t miss a beat no matter what the temperature is outside.

Readers write back

Doug: You seem to be “old school” on the subject of oil life monitors. I used to feel that way, but recent economic conditions have made me reluctant to waste anything! Many have said it’s cheap insurance, but oil isn’t so cheap anymore … not to mention everybody’s time and the environmental issues. And how else would you account for varying conditions throughout the year and throughout the vehicle’s life?

I believe the manufacturers do know how long oil lasts and the sensors and computer allow one to monitor it. Why not take advantage of these capabilities?

If you want a margin for error, you can always use premium oil (not usually worth what it costs) or change at 20 percent. Changing by mileage is either a waste or potentially harmful.

A. Thanks for your point of view on oil changes. I have tried to be clear that I don’t subscribe to a “one size fits all” on oil changes, i.e. every three months or 3,000 miles. I do believe for severe service driving, which is generally the category we fall into around here, going strictly by the onboard oil change monitor stretches the interval out too long. With all of the new oil controlled technology in these engines I want to eliminate any chance of oil sludge.

We see it all the time where a cam phaser fails primarily due to oil sludge and restricted oil flow. So when I see these types of expensive repairs, I believe that makes a more frequent oil change program look inexpensive.

The manufacturer’s obligation is to get the vehicle past the warranty period. What happens after that is up to the consumer. Most of us are driving our cars to 200,000 miles and beyond. The oil change is critical to that happening without major engine repair.

I am a proponent of using a synthetic blend oil, I believe on these newer engines a synthetic blend oil is a must. In fact GM has come out with a new oil called Dexos that will be required in most of their 2011 and newer models.

If a longer interval is working for you and you are not getting any sludging, keep doing what you’re doing. Always be sure to properly dispose of the used oil and oil filter in order to keep our environment clean.

Doug: 1970 Dodge Challengers did not have a coil spring front suspension. They had dual torsion bar front suspension.

A. Thanks for your correction, I got that wrong. While most domestic cars of that vintage had coil spring suspension, the front of the 1970 Challenger, as you pointed out, had torsion bar suspension.

Ÿ Douglas Automotive is at 312 S. Hager Ave., Barrington, (847) 381-0454, and 7218B Virginia Road, Crystal Lake, (815) 356-0440. For information, visit douglasautomotive.com. Send questions to underthehood@dailyherald.com.