Will putting heavier weight oil in my engine cause it to blow if the engine's already on its way out?

Dear Car Talk

Dear Car Talk | Dec 01, 1997

Dear Tom and Ray:

I have an elderly car, a 1987 Pontiac 6000. I took it in for an oil change the
other day, after I noticed a slight clicking noise. At the oil-change shop,
the fellow said he couldn't change my oil because the clicking sound meant
that the bearings were bad, and changing the oil would wreck the engine. He
said my current oil was "lighter," because it was old. He said new, thicker
oil would increase the pressure and make the engine "blow." Is he right? --

TOM: No. He must be one of those M.D./Ph.Ds they're hiring at all those
quick-oil-change joints these days. He probably knows enough to know that
something is wrong with your engine, and he's afraid that if it does blow (by
coincidence) three weeks after he changes your oil, you'll come back and blame
him ... .like his last eight customers have.

RAY: In reality, what you're hearing is probably noisy lifters due to low oil
pressure. And thicker oil would only help the oil pressure at this point.

RAY: If anything, it's more likely to "blow" with lighter-weight oil in there
than with heavier-weight oil. So don't go back to this guy.

TOM: But before you go dumping some 80W-250 sludge in the crankcase, you
should go to a more knowledgeable mechanic and get your oil pressure tested.
Hydraulic lifters are situated far away from the oil pump, and when they make
noise, that's usually an early warning sign that there's not enough oil

RAY: If you test the oil pressure and it's good, then you can rule out a bad
oil pump and bad bearings, and look instead into the possibility of a worn cam
shaft, a bad timing chain, or even something as simple as a bad lifter or a
sticky valve.

TOM: If you really do have low oil pressure, there are three likely causes.
The most obvious is that you don't have enough oil in there, but let's assume
you've checked that. The second possibility is a bad oil pump. The third, and
grimmest, possibility is that your bearings are worn out. And if it's
bearings, you've got a tough decision to make.

RAY: Well, not that tough. It's just a Pontiac 6000, remember. But you do have
to decide how much you love this car, Debbie, and how long you want to keep

TOM: If it's in good shape and you're committed to it for the long haul, you
can have the engine rebuilt for a couple of thousand bucks.

RAY: But if you're ready to get rid of it, or just want to limp along for
another six months or so while you look for another car, then you can just put
some 20W-50-weight oil in there, and keep driving it until it croaks. Good
luck, Debbie.

* * *

What's one secret of financial success? Driving a used car! Read How to Buy a
Used Car: Things Detroit and Tokyo Don't Want You to Know. You can order it by
sending $3 and a stamped (55 cents), self-addressed, No.10 envelope to Used
Car, PO Box 6420, Riverton, NJ 08077-6420.

Get the Car Talk Newsletter