rev up your engines, today I'm gonna tell you why it's not a good idea to flush
the old engine oil in your car, now it's come to my attention lately a lot of
guys would say, hey I like flushing my engine oil every once in a while to get
the crud out, is that really a good idea or my damaging something, well it's not a
good idea especially in modern engines, and to explain why we're gonna have a
little history lessons, now when I was a young mechanic a lot of cars used non
detergent oil, these engines did not have oil filters on them, so the oil had to
keep crud from building up on the soft engine bearings, here's a piston with a
piston rod and this end goes on the crankshaft that has soft metal bearings
they're really soft, they're made soft there's a problem
they'll be degraded, then they can be taken apart and rebuilt but, that was all
fine and dandy with simple cars they built in the 1950s, I've even seen bills
that people had for having their engine rebuilt and it was only like 75 bucks
but today, rebuilding the complex modern engine might cost seventy five hundred
dollars, so you don't want to do any damage to your engine, all modern cars
use detergent oil, if you look on STP bottle, you can see active cleaning
agents control sludge formation and clean key components, they're all
detergent based oil, the old non detergent oil were made so that the oil
would get the bad pieces and it would make them stick on the side of the
engine and the valleys inside and not on the bearings, so these old engines, hey
they build up sludge like mad, I remember taking apart engine that it was almost
like tar in there and you'd have to scrape parts off that baked on the
engine, you don't want to have that happen in your modern car, so in modern
cars with detergent oil and oil filters because those old cars didn't even have
oil filters, the oil filter gets rid of the particulates that are floating in
and anything else will be held in suspension by the detergent oil and
these detergent oils can hold them in suspension for a really long time, some
of those synthetic oils, they say they can last 20 but I never do that, but a
lot of guys will change every 10 and that's perfectly fine
because all the crud stays in suspension and doesn't create sludge on the metal
parts, so the main thing to do with modern cars is, change your oil regularly
so you don't have any problems with your engine, modern designs do not need to
have their engine oil flushed, ever as long as you change the oil frequently
but let's say you bought a used car and the previous owner was a slob, and when
you take off the valve cover you see there's all kinds of sludge
inside, well what do you do then, well of course you shouldn't have bought such a
car in the first place, but here's the problem that can occur with an engine
flush, on an old worn engine sometimes it's the sludge and stuff
that's keeping it from burning oil, it seals the pistons a little bit better
and if you run a flush and it makes everything clean, you might find out it
starts burning oil which it wasn't to it in the first place, and even worse if it
had a ton of sludge in there and this stuff starts breaking it up, if that
sludge gets stuck into little oil galley holes, it can stop the oil flow you could
blow the engine, things will start to burn out the bearings will overheat and
the engine will knock a hole in itself, and in modern engines like this variable
valve timing Toyota Matrix engine, realized that all the hydraulics that
run the variable valve timing, have very tiny little holes especially inside the
solenoids, some of them have tiny little screen filters and if you're running a
flush and pieces start to clog that up, the variable valve timing system can
stop working, I had a customer have one bought it used
thought I'll flush the engine oil, so they did then it started running like
crap, and I told them well you know I ran my scan tool, looks like it has a problem
with a variable valve timing system let me start checking it out, and when I
did he was lucky because first thing I did was I went to the variable valve
timing solenoids that activate them, and sure enough when I took them off the
engine which wasn't that big of a deal, they were all coated with a crud and it
was all jammed up inside, then I had to take that off and then get air
compressor air and blow through all the holes that fed
the engine for the variable valve timing, and did go back to working again but
this car ran perfectly fine before he did the motor flush
he wouldn't about the car was a smart guy, he went out and road tested it and it ran
perfectly fine but after flushing that oil it wasn't running fine anymore, and
another thing that can go wrong with engine oil flushes is this, if it is a dirty
cruded up engine, a lot of times it's that crud that's keeping the oil seals from
leaking, underneath that there may be old crack seals and when you flush it out
and then they get all cleaned out you start leaking oil, you might think
oh Scotty it's just the oil seal it just costs $10, but let's say it's the rear main oil
seal of the engine, what do you got to do to replace that you've got to pull the
transmission off or pull the engine out of the car and it's gonna cost an awful
lot of money on a modern day car, could well be over a thousand bucks, just
realize that modern day oils are really well made, if you change your oil
regularly, hey you're not gonna have any problems, but when it comes to having
the problems in the car and you think you're gonna fix it by flushing the
engine oil out, you might think twice before you try that, because I've seen
guys flush out an engine on a car they're selling because they know it's
all cruded up inside, only to find out once they were done flushing it, now they
can't sell it because it's burning a ton of oil in it and it's leaking out of the
sides, so you might not want to do an engine flush on any car, change the oil
more often and keep it clean, so if you never want to miss another one
of my new car repair videos, remember to ring that Bell!