Put You Faith in Vehicle’s Dipstick, Most Experts Say
Question: I recently had my 1993 Chevy truck’s engine rebuilt. Within the first week, I checked the dipstick and it showed the oil was down half a quart. I took it back to the mechanic who installed the engine, and he told me that the dipstick was wrong. He said he used four quarts of oil, as specified by the service manual. Since then, I have had the oil changed and again found the oil level below normal. What gives?--T.S.
Answer: It is not unusual to have the kind of discrepancy you have found, but most people never notice the problem. It is often the case that dipsticks will not register exactly on the “full” mark when the precise amount of oil specified in the owner’s manual is added during an oil change.
So the question becomes: Do you depend on the dipstick or add the amount of oil specified in the manual?
Mechanics and engineers generally agree that motorists have no choice but to go with the dipstick. If you can’t trust it, then you’d never know when to add oil.
There are many reasons why the dipstick can show the oil level being too high or too low, even when you follow the service manual’s specifications for oil.
It is often impossible to drain out all the oil, either because it takes so long for it to drip out of a cold engine or because the car is on an incline. Sludge buildup in older cars can actually displace the volume inside the crankcase.
It may seem absurd, but not all auto makers use the same assumption when they list the correct quantity of oil in the specification charts in the owner’s manual.
Some manufacturers list the amount of oil it takes to fill a new engine that has never had oil in it before. Others list the amount it takes to fill a “wet engine” that has already had at least one prior oil change.
A variance of half a quart of oil should not matter greatly to the engine. A difference of a full quart, however, is problematic.
Q: I recently purchased a neat 1990 Toyota Camry. The only problem is that the electric fuel pump hums. Some mechanics I’ve asked say that’s normal, but a fried told me it’s starting to go bad. Any advice? --F.T.
A: Most electric fuel pumps hum a little bit. Whether yours is ready to fail depends on how much noise it is making. I’d ignore your friend and follow the advice of the mechanics. If it’s going to fail, you’ll notice the noise getting worse.
Ralph Vartabedian cannot answer mail personally but will attempt to respond in this column to automotive questions of general interest. Write to Your Wheels, Business
Section, Los Angeles Times, Los Angeles, CA 90053. Via e-mail:
ralph.vartabedian@latimes.com.
