Summer blend vs. winter blend in your gas tank

Running winter blend gas in warm weather can cause engine performance problems such as stumbling and, occasionally, stalling. (Dreamstime/TNS)

Q: I understand that the composition of gasoline marketed in the Chicago area is adjusted seasonally (“summer blend” and “winter blend”) due to EPA requirements. Given that many people are driving less during the shelter-in-place, what would be the effect on drivability if you filled your tank shortly before the marketer switched over to the summer blend and, therefore, drove with winter blend deep into the summer season? Likewise, what about the converse situation into the winter season?

R.R., Lisle, Ill.

A: Timely question. Winter blend gasoline has a higher Reid vapor pressure (RVP) to make the engine start easier. The fuel vaporizes at a lower temperature. The RVP is generally 15. In the summer, RVP is usually 7.

Running winter blend gas in warm weather can cause engine performance problems such as stumbling and, occasionally, stalling. Since winter blends evaporate quicker in the summer, they contribute to ozone issues and smog. Even if you only need a half tank or less, fill up with summer blend as soon as convenient. Summer blends are sold from June 1 to Sept. 15. By the time it gets cold, rather than cool, summer blends create less of a problem. Oh, another issue: Prices are also higher in the summer.

Q: In order to unlock my 2014 Captiva door, I had to do it the old fashion way and actually use the key. Upon turning the ignition to start, nothing happened. Battery was dead. Surprisingly, I couldn’t get my key out of the ignition. Also, the battery is only one year old so is there a “home” test I could do to verify a battery draw?

T.K., Montgomery, Ill.

A: It is common for the 2014 Chevy Captiva (and some other GM models) to capture the key if the battery is dead. There is a safety device on the steering column that prevents the key from coming out unless the transmission is in park. If the battery is dead, the device won’t work. If boosting or replacing the battery does help, you may have to replace that ignition lock solenoid. Forget about a home test for your battery. Most auto parts stores and repair shops will test your battery and charging system for free. If you need a battery, they will gladly sell you one.

Q: The Sirius-XM in my Porsche Macan cuts out repeatedly for about three weeks. Porsche service manager says he is swamped with similar calls and says Sirius says that the satellite is malfunctioning. “Refresh signal” has been done three times with no luck. It is impossible to find any info on this satellite issue at Sirius site or anywhere else. Any ideas?

T.N., Chicago

A: If there was a problem with the satellite signal dropping out for weeks at a time, we certainly would have heard about it. Yes, it can drop out momentarily when driving through a tunnel or in the city with tall buildings, but the signal usually buffers and picks up where it left off. I have a hunch the service rep is trying to create a buffer of his own.

Q: In today’s column, a reader asked what could be done to prevent the bad exhaust smell from a neighboring vehicle from entering the reader’s vehicle. I turn on air recirculation feature until I am past the offender.

D.B., Asheville, N.C.

A: Hah! Simple solution to an annoying problem, switch the HVAC to recirculate.

Send questions along with name and town to Motormouth, Rides, Chicago Tribune, 435 N. Michigan Ave., Fourth Floor, Chicago, IL 60611 or

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