Gas Octane Ratings Is Higher or Lower Better How Octane Affects Your Car or Truck

In this video, we're going to go over octane, high octane, and low octane, the differences in what it does to performance on cars' engines, and maybe break a few myths of what you think you know and what you don't know. All right, so we're going to do it on the board here, explain it, just so it makes a little bit more sense to you.

So octane, you get your three major octanes, this is what you see at all gas stations, right? So you have 87, 90, and 93 octane. Just going to break it down for you what octane means. So it's a compression ratio, right? So your cylinder has compression. That's what gives it the power because it ignites, the piston goes up, pushes back down, and there's an explosion, crank turns, and away you go. That's basically the way it works. So put it in these terms this is your cylinder head that's your cylinder your piston, spark plug's there. So if you have high octane the detonation on it actually is sooner than later. So you have a shorter more power stroke. It gives it really faster turning. So the crank turns faster, shorter ratio of that long that piston going up into that cylinder and back down.

If you put in low octane in a high-octane engine it has to compress all the way up here before the detonation happens and then it comes back down. The problem with that is electronic timing, computer timing, nowadays that has been programmed for a faster air-fuel ratio so that the compression timing is on if you use low octane, that detonation is going to happen later than sooner. Now that's what I'm saying. The computer is like, "What's going on, we're not coming back down as fast?" Eighth of a second or 3.5 seconds you're coming down at 5 to 6.5 seconds. So the timing is off. When that happens you hear a clanking noise during you hear a clanking noise. And that's like in the old days we would say you've negative the timing or positive the timing. You can manually do that but now the computer does it for you.

If your car calls for high octane, you have to use it for that reason. And what happens long term this piston goes up and down and instead of having a round cylinder chamber you end up with an oval cylinder chamber and that voids the warranty. You also can crack valve seats which is a long explanation I'm not going to get into it. But real simple horsepower, say you have a car that is 350 horsepower with high octane, you put low octane in it can drop down to 320 total horsepower and that's due to the timings being off.

So you could ask yourself what's the difference to $3 a gallon to $3.20 a gallon when you have a 15 or 20-gallon gas tank what are we talking about? A whole $2 maybe, you wouldn't hesitate to spend that on good coffee. So you bought that car, you pay that car bill, you want the performance.

Now let's talk about having a low-budget car and what I mean low budget I just mean a car that calls for anywhere from 87 octane. If you put 93 in it you're not doing anything, you're literally throwing your money out the window because that car is not designed for the 93 octane. It won't change, it won't become Arnold Schwarzenegger, it won't become stronger. It can't, it's mechanical, it only knows what it knows and what it's been programmed for and what it was built for. You will not run cleaner, you will not get better gas mileage. But what you will do if you put that low octane in a high octane car, you will lose gas mileage, you will lose horsepower, you will lose engine performance.

It's there for a reason. So don't forget, check your manual and look on that gas cover lid. So say we have a V6 or V8 so you get your cam over here, sometimes you might have dual-cam and then you have your crank, okay? So timing chain or belt, more than likely a chain if you've got a performance car, goes up and over the cams and down. And what happens is you have your valves are up here. This is your crank which is connected to your pistons. So I'm going to just draw a little connecting rod and then a piston head in the chambers. These cams are up here, like I said, the valves are up there and this goes back and forth this way. Every time this crank goes up, pushes the piston up compression, spark plugs are usually up here so you get your spark plugs. Now if you put in low octane gas and you're supposed to have high octane, what happens is the compression stroke is higher up, instead of detonating down here it's going to detonate up here. That's going to cause the timing to be off because this chain is supposed to be timed perfectly in a magnetic timing going around and sends it back to the PCM, tells it when to do the air-fuel ratio, how to mix it.

If that is firing too late it's gonna adjust, the computer's gonna say, "Hey, we're not going on the time span we're supposed to be going on. So I'm gonna send the timing back. I'm going to put it in the negative form instead of the positive form." And that's going to make your valves clank, it's going to have an engine clank and that could crack a valve seat. It will also cause that piston, like I said, the detonation to start to ovalize the cylinder head instead of a round cylinder head. If you think you're going to get away with it, you're not because a trained technician is going to tear your engine apart if your engine breaks down and they're going to say so sorry you didn't use the proper octane. Because how do you know that? Because we can tell by the way the cylinder head looks and you've cracked valve seats because your timing was off and you couldn't mess with it because it's computer PCM. It's all in the pudding.

So here we have the old school car. This car was actually made for leaded gas. Some of you might not have heard this, but there used to be leaded gas. And until the early '70s they came out with unleaded gas and what that did was I don't know, I'm not a scientist. But it was made for leaded gas. It ran good on unleaded gas, but that's why they sell octane in a can for cars that have these big engines in it with the old carburetor compression. But what I want to tell you is that this had to be manually adjusted, the air-fuel ratio and the timing had to be manually adjusted, not computer adjusted. So when you put bad gas in this car or if it sat around for a while and you start it up and you try to adjust the air-fuel ratio it's going to adjust to the low octane that you have in it or the high octane. Then two tanks later you fill it with high octane or you put an octane boost in this car. You better adjust that air-fuel ratio and the timing again because it's off. And not to mention back then you couldn't find a label for octane because the gas cap is back here.

So here we have a car that calls for E up to E15 gasoline only. E stands for ethanol. So when you're at the pump and you see ethanol 10% this vehicle will only allow you to go to ethanol 15%. Anything above that it's a no-go. Here we have a European car which says right on the door, really nice, requires 91. So this happens to be Mr. Andy's clunker.

Oh hey.

He rides around when he's not driving his Porsche. Now he has an old Porsche, I think a 1984 Porsche. And that one calls for a high octane also and he was just saying to me, "Wow Sue, if I don't put 91 octane in my Porsche, boy do I know it. That thing loses power, it's missing, it just doesn't run right." He goes, "I can get away with it like every other tankful or every three tanks I can put a good premium in this. My BMW, no big deal." You don't really see the gas power difference in the engine performance. But don't make a habit of it because if you fill this thing constantly with low octane and not 91 you're gonna hear it in the engine and you're going to lose the horsepower.

So here we have a newer updated American car and they have it posted right on the door. It actually says also to show us the manual, but it says can use E85 gasoline but do not use additives. You can't put an additive in when you have up to E85 and it doesn't even have a gas cap. Now here we have to the obvious eye a diesel. Diesel, if you don't have one and you've never seen one, the gas tank opening is just like the old school days when they had leaded gas. There's no restriction, there's no flap in there like you see nowadays on your unleaded gas tank. So a diesel tank pump nowadays does not fit in a regular gas engine. But the old days, when you had wide-open hole you could put diesel or gas in there. And if you put gas in a diesel engine, oy almighty you're going to run into some problems, burn the pump out, glow plug, it's not gonna be pretty. You can't put diesel if you ever mixed it into a gas. I wouldn't recommend putting a full tank in but if you use the same gas can and there was some diesel fuel in there it's gonna run rough, it's gonna pit and patter but eventually, it'll clear itself out. You probably won't cause much damage, but if you put gas in this it's not going to be pretty. So there's the flap for a regular gas, which you do not see in a diesel tank. so the nozzle is a different size nowadays where in the old days it wasn't, it was the same opening for unleaded or diesel.

So here we have a performance car, right? And the gas cover says, "Premium unleaded only." What does that mean? Ninety-one, 93? So what you need to do in this case is check your manual and it should give you the exact octane required. So let's check the manual. Let's see. So I'm going to go to the index first and you're going to look up fuel. So let's look up the fuel. All right, so here it says, "Use unleaded premium gasoline with an octane rating at least 91." And then it also says, "Do not use E85 fuel." Which I covered earlier about E85 means that you can have ethanol up to 85. So that's usually common in the Midwest for us in down South not so much in the Northeast. And that's pretty much it. So it's right here, pretty easy to find. That way you know you're running your car on the proper fuel to get the most out of the performance.

So hopefully you enjoyed this video. I know I enjoyed making it for you. Hopefully, it just gives a little bit better explanation of the differences between octane and all the myths that come with it. Thank you for watching. If you're not a subscriber please subscribe and don't forget to ring that bell because then it turns on all your notifications so you won't miss a future video.