Grainews had a few automobile questions roll in, so we’ve revived Jim Kerr’s Backyard Mechanic column. If something has you stumped, send in your question.

Send us your questions

Do you have a question for the Backyard Mechanic? Email your question to the editor, Jay Whetter, at [email protected] fbcpublishing.comor mail it to “Backyard Mechanic question,” Jay Whetter, Grainews, 1666 Dublin Ave., Winnipeg, MB R3H 0H1.

Question

Dear Backyard Mechanic:

At my local auto parts store the other day, they told me that once you use synthetic oil you cannot go back to conventional oils. He vaguely explained it was due to the change in the engine with synthetics. I have never read this was the case and would like to go back to cheaper oil. Any truth to this assertion?

Thanks, Frank.

Answer

I know of people who have switched back and forth several times with no problems, including me! It is not recommended to mix different brands of oils because they may contain different additive packages, but it can be done too if it is the necessary. It is better to mix different types of oil than it is to operate an engine low on oil. As for changes in the engine, I can think of nothing mechanical inside the engine that would change because of the type or brand or oil used in it. Some oils are designed for older engines and may contain seal conditioners to soften old seals so they work better, but even if you changed to a different oil, it wouldn’t harm the engine. As long as the oil and filter are both changed, so you are changing almost all the oil in the engine, go ahead.

There are advantages to synthetic oils, such as easier starting in cold weather, less wear during cold starts because the synthetic oil flows easier when cold compared to a conventional all season oil, and better engine protection when engine temperatures go up or the engine is under load. Conventional oils tend to thin out when temperatures rise, while synthetics maintain their viscosity much better.

The only disadvantage of synthetic oils is cost. If you decide you want to go back to synthetic oil at the next oil change because of different driving conditions, it isn’t a problem. In my own vehicle I have switched between synthetic and conventional oils several times as I tested different types and brands of oil. Oil analysis has shown no problems with mechanical wear at any time, but I do notice the ease of starting in winter when using the same grade of synthetic as a conventional oil. If you want a lower cost and some of the benefits of synthetic, there are synthetic blends — a mixture of conventional and synthetic oil that are available, too.

Question

Dear Backyard Mechanic:

I have a 1988 Olds Delta 88 car. The transmission has been overhauled, but it doesn’t shift into reverse very well. I wonder if you have an idea what’s wrong.

Thanks, Walter

Answer

The first item to check would be the adjustment of the cable shift linkage. The shifter cable has an adjuster with a U-shaped collar on it. Lift the collar up (it will be brittle with age so be careful) and then place the transmission manually Neutral. Then the shifter should be placed in Neutral. Pull the two sides of the cable adjuster apart to take up any slack in the cable and then push the U-shaped collar back down to lock the adjuster in place.

If the linkage is adjusted properly, then the problem is likely related to the reverse gear application in the transmission. Reverse gear uses a band to hold a drum from rotating. This band is applied by a servo (piston) that moves in a bore in the transmission case. If the servo is sticking or the seals on the servo are not properly in position, then the band can’t apply properly and reverse gear doesn’t engage properly.

The reverse servo is located under a round cover on the top of the transmission case and can be removed from the transmission without disassembling or removing the transmission. The problem could be with the band itself, but I doubt it as the transmission has been overhauled.

Finally, one of the valves in the valve body may be binding, causing reverse to shift poorly. This would require removing the valve body from the transmission to inspect it, but a binding servo is a much more common problem so I would go there before looking at the valve body.

Question

Dear Backyard Mechanic:

Editor Jay Whetter here. I have 17-inch all-season tires for my Chrylser Pacifica 2WD. I also have 17-inch winter tires and rims, but it turns out that I could have bought 16-inch winter tires and rims and saved a bundle. Is it OK to run 17-inch wheels in the summer and 16-inch wheels in the winter? Do I have to do anything to reset the speedometer so it knows I’m using smaller wheels?

Answer

For most vehicles, there is no problem going to one inch smaller rims to install winter tires. The only thing to check is the clearance to brake calipers and rotors. Because 16-inch wheels came on some Pacificas, I can’t imagine it being a problem on your vehicle.

As for tires, buy winter tires with a taller sidewall than the summer tires, For example, your summer tires might have a 55 or 60 aspect ratio and you could install winter tires with a 70 or 75 aspect ratio. What this does is make the outside tire diameter the same for both the winter and summer tires, so there are no problems with incorrect speedometers or computer programs. The tire shops have catalogs that indicate the number of revolutions a tire makes per mile, and they can find a tire that will keep this the same.

I have done this on my wife’s car. It came with 16-inch wheels but some models had 15 inch. I put winter tires on 15-inch rims. The taller sidewall also provides more cushion against impacts on rough winter roads and potholes, and you are correct — it is often cheaper to install the smaller rim and find a tire that fits correctly.

Jim Kerr is an automobile writer based in Saskatoon.

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