Q. On a recent road trip to South Carolina, we came upon many different places to get gas. On a few occasions we stopped at Sheetz for gas. My question is about the different octane choices at the pump. My Subaru uses 87 octane, but there was 88 octane that was available and was at least 10 cents cheaper, yes cheaper, than 87 octane. I was a little hesitant to try the higher octane, not knowing if it was okay to use. Any thoughts on being able to use this fuel in my Subaru? A. The 88-octane gasoline sold at Sheetz is 15 percent ethanol rather than the 10 percent ethanol that is in most gasoline. Most cars made since 2001 can use E15 gasoline without any issues. Subaru models vary a bit. In most models you can use reformulated gasoline with up to 15 percent ethanol, but with the 2. 5-liter engine, Subaru states to use gasoline with only 10 percent ethanol. In my own car I have tried E-15 gasoline. The car ran fine, but I found fuel economy went down slightly. Q. I replaced both wiper blades at the same time. One wipes clean, the other streaks. Is there a product that rejuvenates blade quality? Good quality blades are not cheap, and I would prefer not to buy another set. A. Alcohol wipes can do a decent job of cleaning wiper blades and can restore some life. The streaks or chatter can sometimes be related to the windshield. I recently used a glass cleaner and water repellent. The glass was clean, but the wipers chattered. The issue could also be the wiper arms. The wiper blades should be perpendicular to the windshield. Sometimes a slight tweak to the wiper arms can solve blade streaking. Also keep in mind most wiper blades near the end of their useful life in about a year of use. Q. I decided to check the front brake pads on my wife’s 2016 Toyota RAV4 with 42, 000 miles because she has a heavy foot. I was surprised there was little rust, which I assume is because the RAV4 is housed in a garage. I noticed the inboard pads had about 40 percent of the pad left. And the outboard pads had 70 percent left. Is this normal since the caliper piston pushes directly on the inboard pad? Anyway, I rotated the pads, thinking of all the money I will save. Is there any downside to rotating the pads? A. The uneven pad wear may be a result of sticking caliper slide pins. Chances are you may have added a little brake grease to the slide bolts when you swapped the pads. As for any issues, other than a possible squeak, I do not see an issue. Many years ago, I owned an MG-B and the owner’s manual recommended as a normal maintenance to switch the inner and outer brake pads to equalize wear. Q. My father owns a 2020 Mercedes E 350 4matic. He is the original owner, and the car has 37, 000 miles. My father is getting older, so I have started helping him take care of his car. We recently went to the dealer for an inspection, and oil and filter change. All went well and Mercedes recommended a few other services. They recommended replacing the air filter, four spark plugs, and transmission service. We held off on the spark plugs and transmission service which we will do in six months at the next oil change. We were quoted a price of $550 for the spark plugs and $ 1, 400 for the transmission service. I did not get further details. I own Honda and Acura vehicles, and the fluid changes are very straight forward drain-and-fill and I have no issues performing it myself. Do you know if the Mercedes is a drain-and-fill and if so, do you think it is a DIY service? Also, what do you think about the quotes? A. The spark plugs are a little pricey, with a suggested list price for Mercedes spark plugs at about $45 each and about an hour labor to replace them. I am seeing labor rates vary across the country with some dealer rates up to $260 per hour. The transmission, differential, and transfer case fluid should all be changed around 50, 000 miles, according to Mercedes service. Also the torque converter has a drain so you can change all of the fluid. The fluid is $30 a quart and you need about 11 quarts. The labor time to change the fluid is 2. 5 hours, and there is no drain plug you need to take down the pan. The bigger issue is you need a special tool to refill the transmission. The spark plugs are an easy DIY project, but I would leave the transmission service to the dealer.
https://www.boston.com/cars/how-to/2025/11/24/car-doctor-comparing-87-vs-88-octane-gasoline/
Comparing 87- vs. 88-octane gasoline
