- A lot of people can tell you what makes an engine more powerful. You can look at the displacement, you can look at the compression ratio, the amount of boost it
makes if it's turbocharged. You can get a pretty good
idea of how much horsepower in engine should make. But what makes an engine more reliable? What are the pieces that
contribute the most to reliability? And what things do the most
reliable engines have in common? We looked at a ton of
engines, talk to mechanics, drove through junk yards and
today we're gonna show you what we found out, what
the most reliable engines have inside them, and
then we're gonna tell you how you can get an engine to
go a million miles, let's go! (energetic upbeat music) - A big thanks to Keeps for
sponsoring today's video. Thank you Keeps. - Uncle Jerry, I'm heating up your soup. - Thank you, nurse Nolan. - I'm not your nurse uncle Jerry. - Mmh, he's a peach. Ah, help, nurse Nolan could
you help me out please? Okay, calm down Dave, calm down. Ever since I took Dave out of the basement he's been eyeing my melon like
it's one of his precious ex. I told him, "This is no egg, Dave. I just happened to be one of
the two out of the three guys to experience some form
of male pattern baldness." But he wouldn't listen,
that's deep flesh wounds. Maybe if I were to use Keeps,
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you didn't know that number. Hey, nurse Nolan, forget the soup, I'm ready for my sponge bath. - [Nolan] Oh! - Or you might've heard of
someone blowing a motor, and that is a pretty broad term, but to put it simply a
blown motor is any damage that is severe enough to require an engine rebuild or engine swap, when it comes to reliability
and damage over time, the biggest culprit of these failures is some form of overheating. Overheating it can warp metal
components in an engine, it can melt or wear out gaskets and it can cause high pressures
and spots not designed to stand up to those pressures. So to combat overheating and
engine has two main methods, good cooling and good oiling. Coolant gets chilled in
your radiator then flows through the engine, cooling the metals and gathering heat to take
it back to the radiator, to be cooled again. The pathways for the
coolant have got a cool the entire block, not just
the first few cylinders. And engines like the Toyota
3VZ, the coolant channels are a little too small and
in slow speed applications like off-roading, the
radiator would struggle getting the coolant cool enough and it would be too hot by the time it got to the furthest cylinders. That made for a pretty
common failure point in the 3VZ's original head gasket. But the oil also prevents overheating. Engine oil is a lubricant between
metal parts in the engine, and a lubricant reduces friction
between those two metals, which means less heat. Now engines that have high
coolant and oil capacities tend to be some of the longer
lasting, more reliable engines. Think about it, if a small engine loses a quarter liter of oil, it's
gonna have a bigger effect than it would on a bigger engine. Bigger engines got more oil, so that loss of oil has less
effect on the total volume of oil in that engine. But it doesn't mean that you
can't have a good small engine. Honda's F series and even Toyota
is 22RE, I used to have one in my Toyota pickup truck,
frigging love that thing. I drove it without oil for a long time. Hey, if you know where
my truck is calling me I want it back, my sister stole it. And one of the other things
that can affect oiling is actually your fuel. Have you ever noticed
that diesel engines tend to be more reliable than petrol engines? That's because petroleum-based
fuel is a detergent, it cleans the microfilm of
oil off the cylinder walls and then as the piston
goes back up that oil is no longer there, but
diesel fuel actually acts as a lubricant and eases
the wear on the pistons. Engines like the Mercedes OM617
and the Volkswagen 1.9 TDI can easily do over 300,000 miles. But overheating is not the
only way that temperature comes into play with engine reliability. I'm talking about thermal expansion. Now an engine has two main
parts to it, it's got the head, it's got the block, the head
is where the valve train is, and the block is where your
piston rods and crankshaft are. In between them is the head gasket, ahead and block are two separate pieces so that the engine
internals can be assembled. If it was just one piece
you'd never be able to get your pistons in there. So it's gotta be two pieces and the gasket in between those two pieces has gotta be really good to prevent leaks. So now that you know that
we got these two pieces what material do you make them out of? And you can make them out of cast iron, it's strong and cheap,
but it's really heavy and it doesn't dissipate heat really well. Or you can make them out of aluminum, it's lighter and it's better
for cooling, but it costs more and it expands more when
more heat is put to it. It's like a thousandth of an inch, but it's enough to get the precise parts of your engine rubbing against each other. And overheating cylinder
can cause the pistons and rings expand and
damage the cylinder walls. And then when the engine cools again, you got more space there
and you lose compression and start burning oil, that's all bad. Aluminum expands more than
twice as much as cast iron with the same change in temperature. It's because of this that
some very reliable engines have an iron block, but in aluminum head, you get the heat release
of the aluminum in the head with the rigidity of the iron block. This is obviously the
best setup in any engine with an iron block and an aluminum head should be good to go, right? Wrong, some of the least
reliable engines of the world are also iron block and
aluminum head combos. It all comes back to thermal expansion, as the engine heats up to
normal operating temperatures the block and head expand
at two different rates because they're made up
of two different metals. Then when you turn the
engine off they cool down at different rates as well. This starts to create a grinding
effect on the head gasket and over time it gets weaker and weaker. Engines that have this issue can be fixed with a really strong head
gasket, but if you're looking for top tier reliability
you'd want an iron block and you'd want an iron head. But while all this is going
on inside of the engine there are some telltale
signs outside of the engine that can show you if your
engine is reliable or not. Picture a four cylinder engine, as pistons one and four go down, pistons two and three, go up. The inertia of the pistons going up is the same as the inertia
of the pistons going down. They balance each other out,
now picture a V6 engine. Here no pistons are up
and down at the same time, pistons one and two, they're connected at
the same crankshaft pen, and as they come up one after the other, the other four pistons are mid stroke and that makes this engine want to shake, this is called harmonic discordance, and it comes from an imbalance
in the primary forces caused by the pistons. Inline foreign engines cancel
out these primary forces, reducing vibration and
therefore reducing wear. But they're not perfect,
there are secondary forces and these are caused by the
piston movement in the cylinder. So when a piston goes up and
down it actually travels faster in the top half of the cylinder than it does the bottom path. So at halfway through
the pistons movement, it has moved half the length of the stroke plus a little bit extra. The primary forces are balanced, these secondary forces they are not. An engine like a straight-six
has both the primary and secondary forces balanced. Because of this, some of
the most reliable engines are straight-sixes,
the Plymouth Slant-Six, the AMC inline-six and the Merc OM606 can make it to 400,000
miles with good maintenance. So if we take everything we've learned, large oil capacity, inline-six,
all iron construction and diesel lubrication, and
we searched for an engine with all those traits, what would we find? We are looking at the all iron
straight-six turbo diesel, the Cummins 6BT 12 valve,
this engine is so reliable, it outlasts the trucks that it comes in. Cummins actually has a million mile club, they send you a new cap plate
to stick it on your truck once you reach that million miles. It's kind of like our
own donut underground where we'll give you free
stickers every couple of months with a bunch of other cool bonus stuff, you get to watch some behind the scenes of B2B and all other shows. - Do you need Alexis first aid kit? - [Man] Wow, I bet those
bandaids are expired. (chuckling) - Listen, they're not, I don't
think bandaids expire, right? That's not a thing that's expirable. Do you wanna join? Hit that join button down below. So it looks like our theories work though. We took all the parts that
make an engine reliable, put them in one engine
and came away with one of the most reliable engines on the road, that was pretty easy, almost too easy. What if I told you that
there was an engine that has gone hundreds
of thousands of miles, some well over a million
miles and it has almost none of the reliability markers
we just talked about. It's Toyota's V8 from the 90s and 2000s. The beast inside the
famous million mile Tundra, in the engine, in my GX470, the 2UZ-FE. Now for those of you
who don't know in 2016, Toyota Tundra owner Vic Shepard
was given a brand new truck from Toyota in exchange for his 2007 model that had over a million
miles on the odometer. But the 2UZ is nothing like
what we described as reliable. Cross playing V8 like the 2UZ
need a weighted counter shaft to balance out those primary forces. It's still balanced, but it
adds weight and lowers peak RPM. The 2UZ also has half the oil
capacity of the Cummins 6BT. And it's also got an iron
block with an aluminum head. So how in the heck did this engine make it past a million miles? Is it really good maintenance, or Toyota's just super over engineered? Well, yeah, it's those
things but it mainly has to do with engine cycles. We measure an engines lifespan by miles because that's really the
only metric that we have. And it's that part that
we as drivers care about. But for an engine the true
counter on its lifespan is engine cycles, when you
start the car to drive to work, the engine is cold, it
works just a little harder to warm itself up but then it's cruising along at operating temperature. And once you get to work, you
park the car, you turn it off and then the engine cools down. Once it's cool again, that's one cycle and when you drive back home
from work, that's another cycle and each cycles, the
metals expand and contract. But they don't really care
how many miles you drive in between those cycles, whether
your commute is two miles or 200 miles, it's still only two cycles. Now, Vic Shepard's Tundra was a 2007 and it was gifted to Toyota in 2016 which means our buddy Vic
drove 125,000 miles a year, that's 10 times more
than the average person, but it's still only 10 years
worth of engine cycles. Maybe even less, because if
you're driving all day long your engine doesn't always
have time to cool down. Start up and cool down are the
hardest times for an engine. If you've ever taken a warm
glass out of the dishwasher and put ice water in it, there's a chance it
shattered right in your hand, the rapid change in temperature contracts the glass weakening it. And the more drastic the change,
the more stress it's under, well, that's exactly what's
happening in your engine. And that's just not the block in the head that's all the components. So even though this Tundra
engine made it 1 million miles it had gone through the engine
cycle of 120,000 mile car. Now the 2UZ it's still
a dependable engine, forgetting engine cycles. It's got really good cooling, it's got very strong head gasket, so they can still go
a long way regardless. And there are other engines
of all kinds of configurations and sizes that are
exceptions to these rules. But on top of the engines
own parts use case is an important part of
calculating engine reliability and longevity, even if you have
a quote "bulletproof engine" how you use it is going to
make all the difference. But at least now, you
know exactly what you need to choose a reliable engine
for yourself and keep it going till the end of time, or until
you give it to your sister and then she sells it out from under you. Let us note down in the
comments what we should swap into Pumphrey's AE86,
they pulled his engine out and money pit if you haven't
seen it, check out that episode follow Donut Media on Instagram
and Twitter @donutmedia. Follow me on Instagram @jeremiahburton. And until next time, bye for now. (soft upbeat music)
