Question: Is it better to maintain my engine's oil level
at the full mark or wait until it reaches the "add"
mark to add oil?
Answer: Most vehicle manufacturers say it's okay to wait
until the level reaches the add mark to add oil. The add mark
But
considering that the crankcase capacity on most passenger cars
today is only four quarts, running the engine 25% low on oil (one
quart) may not be wise. Here's why.
Oil not only lubricates the engine's internal parts, but also
helps cool the bearings. The total amount of oil in the engine,
therefore, serves as a heat sink to help control heat. Under
normal driving conditions, running a quart low probably doesn't
make much difference in terms of bearing temperature or overall
engine lubrication. But during extremely hot weather, when driving
at sustained highway speeds and/or when towing a trailer, running
a quart low may increase the risk of accelerated engine wear and/or
damage.
The best advice, therefore, is to add oil whenever the dipstick
reads low. Don't wait until it is down a full quart. If it needs
half a quart, add half a quart to bring it back up to the full
mark.
CAUTION: Do not overfill the engine. Adding too much oil
can overfill the crankcase. As the crankshaft spins around, it
can whip the oil into foam if the level is too high. This, in
turn, can cause a drop in oil pressure and loss of lubrication
to critical engine parts. Also, too much oil may cause leaks
as the extra oil is forced past seals and gaskets.
Follow your vehicle manufacturer's guidelines for the type
and viscosity of oil to use in your engine.
