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!
