Octane Ratings and the 4 Stroke Engine Cycle

[outdoorsman310]

2 strokes have a power stroke every stroke!

[daSpidy84]

as always, extremly helpful! constantly learning with your vids, you make things easy to understand, even for dummies like me, lol thanks!

[808mokunuibulli]

Hey eric been watching your videos for awhile now, and was wondering if you had a video for fuel injectors? I got civic swapped gsr and it seems to be running rich and thought maybe my injectors were dirty or just needed to be changed.

[fladdy45]

So, higher octane, higher compression ratio?

[tubejim101]

@fladdy45 The higher the octane number, the more compression the fuel can withstand before detonating.

[R4nD0mus3rNam3]

Hi Eric, i have a 1991 ford aerostar and i been using 93 instead of 97. doing this damages my motor? will my MPG improve if i use 97?

hope you can awnser.

and thanks for your videos

[EricTheCarGuy]

@R4nD0mus3rNam3 Does it call for 97? I don't think it does honestly. Run what is called for by the manufacture and you should be just fine.

[R4nD0mus3rNam3]

@EricTheCarGuy thanks eric, i cheked the manual and the first thing i noticed is it said 87 but in my country there is only 93/95 and 97, then i cheked on the internet and lerned that there are diferent ways to grade the octanes. so the 87 of USA is equivalent to 95 in Chile

[EricTheCarGuy]

@R4nD0mus3rNam3 You are correct as the octane ratings in the US are done by API which is the American Petroleum Institute. Come to think of it I wish I had mentioned that in the video. Thanks for the comments.

[flchaptersdmf]

I've been told if you use 87...you should use 91 to clean the tank out?

[EricTheCarGuy]

@flchaptersdmf Nope, they just want to sell you expensive gas.

[EricTheCarGuy]

@srtxsara ALL engines have overlap, it helps to draw in the air/fuel mixture.

[TeDuaMalakie]

i think it's called the Otto cycle !! thanks for this priceless video ! .

[EricTheCarGuy]

@TeDuaMalakie Never heard it referred to that way before, thanks for the comment.

[SuperMegaCliff]

What about using TOO high of an octane? Say I put 91 in my car that calls for 87? is that just a waste of money?

Anyways, great video. Wish I had a dad around that knows as much as you do about cars. Then I wouldn't have to got to school for this!!! haha

[EricTheCarGuy]

@SuperMegaCliff Yes, if you put 91 in a car that takes 87 you are wasting your money. Thanks for the comment.

[dublistener]

Thank you for this video, I just have one question though.

I'm looking to buy an Acura RSX Type-S, and it says that premium fuel is recommended. Will it harm the engine if I use lower octane fuel instead of paying more for the premium? And will it hurt the performance by much? Thanks

[EricTheCarGuy]

@dublistener If it says premium you should use it, if not performance will be compromised for sure but it would probably take some time before engine damage resulted if at all, the main point would be that you would not be able to get all the engine can do if you used regular gas.

[DARKSCOPE001]

thank you for doing this video I hate when people think that octane means heat value produced by the fuel. When I was in aviation school the first thing we were taught was to forget that because the lowest grade avgas we used was 100ll it produces no more heat than the cheep stuff i put in my car. I cant tell you how many people think high octane makes an engine more powerfull its funny. Anyways man I love all your videos you do a great job and i love watching all of them i learn so much.

[EricTheCarGuy]

@DARKSCOPE001 Yea that bugs me too and is the main reason I made this video. Thanks for the comment.

[DARKSCOPE001]

@EricTheCarGuy yea i always love when i tell people that most aircraft fly off 100ll and we go all the way up to somewhere like 130 140ish. Had some ricer kid I work with want to know if he could buy avgas to put in his car. I told him first off its leadded and second off why? it probably wouldnt even combust in a car engine. I always love the people who buy a bottle of octane booster. Every time I see it I want to ask. So do you really think this makes you go faster? or are you buying snake oil

[EricTheCarGuy]

@DARKSCOPE001 So many things in the automotive universe are based on that very mentality. Thanks for your comments and input.

[DRIFTINGIN808]

Eric, why does Race Fuel add so much power? is it because you have less pre ignition causing the the cylinder to go up further and giving it a longer power stroke?

[EricTheCarGuy]

@DRIFTINGIN808 Because it allows for a higher compression ratio or more pressure from forced induction, Race Fuel is often over 100 octane. More compression or more boost equals more power, just using the fuel does not necessarily give you more power it just allows you to make more power.

[w8ting4fri]

hey i have a question. you said that atmospheric pressure forced the fuel into the cylinder, but isn't is the pressure behind the valve caused by the gas being pumped in behind it ?

[EricTheCarGuy]

@w8ting4fri Nope, if it's a naturally aspirated engine it's atmospheric pressure that is filling the void created by the cylinder moving down in it's bore that draws the air fuel mixture in, the gas is just along for the ride and contributes nothing to the inflow of the mixture.

[w8ting4fri]

@EricTheCarGuy what do you mean by atmospheric pressure? do you mean the weight of the atmosphere on the engine?

(sorry to be annoying but im very curious)

[EricTheCarGuy]

@w8ting4fri That's exactly what that means, atmospheric pressure is higher at sea level than it is in the mountains because there is less air pushing down at higher altitudes and more pushing down at sea level, similar to the ocean where the deeper you go the more pressure there is, think of the atmosphere as an ocean of air.

[vietcong4u]

thank for the reply eric..... I have a couple question is not about mechanical stuff but i wonder do you have any good tip for me how to find a water leak in my car? (01 accord) driver side soak wet when rain.... Should i hook up a smoke machine in side the car and try to fine the hole? lol

[EricTheCarGuy]

@vietcong4u That's not normally how it's done, you usually get a garden hose and run it while you look for leaks in the effected area. That said I've seen a lot of leaks caused by poor windshield sealing which sometimes happens when a windshield is replaced.

[vietcong4u]

so when you hear your engine knocking while go under-load or try to go up a hill what is that mean? is it the fuel i and the air ignite to early before the piston Rich the top

[EricTheCarGuy]

@vietcong4u That is usually what it means yes and if you let that go on for long enough you can seriously damage your engine.

[Ko32St]

I Think Michael Jackson Is Back There Too LMFAOOO!!!!! J.K

[harplus3]

hello. thank you for your informative video!! I learned a lot about what octane is. being a newbie to this its like being spoken to me in greek!! I have a question for the video creator or anyone else. I have a 2005 dodge dakota. i use 87 in the tank. just out of curiosity, what would happen if I were to put the 93 octane fuel in the tank? just curious. thank you

[EricTheCarGuy]

@harplus3 Your wallet would be lighter but that's about it.

[harplus3]

@EricTheCarGuy haha thanks man sounds good!

[ricardoc2659]

So is it a good to have a lot of octane or just what ever the car or truck can get ?

[EricTheCarGuy]

@ricardoc2659 Unless the owners manual says you need to use it you don't need it.

[davidzzz94]

Also, does this also mean that octane rating has nothing to do with the quality or how clean the gasoline is?

[EricTheCarGuy]

@davidzzz94 Octane ratings are done by an independent organization (API), not by the oil company therefore the ratings have nothing to do with the quality of the fuel.

[davidzzz94]

so eric! from what range of compression ratio do you recommand for each range of octane fuel?

[EricTheCarGuy]

@davidzzz94 To be honest it also depends on the combustion chamber design as well as some other factors but as a rule I would say when you get up in the 11:1 ratio high octane would be required. Mid-grade is mostly just a marketing point as I don't know of any car that calls for mid-grade, I've just seen Premium or regular unleaded requirements.

[ritual45man]

Hi Eric,

The compression ration of the diesel engine is much higher than the gasoline engine. Does that imply the diesel has octane rating higher than the gasoline?

If so, then, can we mix some diesel to the gas tank to make the octane rating of the regular gas higher?

It this work, then it should be much cheaper than buying high octane gas for the old car. Am I crazy?

[EricTheCarGuy]

@ritual45man Excellent question! I know it's counter intuitive but diesel is actually rated at 15-20 octane, the reason, you can't compare diesel to gas as they are completely different fuels that work in completely different engines. I don't have the space to get into the specifics here but you might google diesel and gas to get a better idea of what I'm referring to. BTW you should NEVER put diesel in a gas engine, or vice versa, bad things will happen.

[cp120x]

@ritual45man I won't go comprehensive here but Diesel work the total opposite of gasoline. Since diesel is heavier and harder to ignite, you don't need to "hold" ingnition as for gasoline but somehow help it to start burn. Diesel will refer to cetane index, not octane. Not for the purist but you can an consider cetane as an ignition promoter... Diesel and gasoline are too far on their chemical characteristics to simply mix them and get something usable.

[switchgrassfuel]

I was wondering would it help to run E85 or E50 at a higher altitude because Ethanol has more oxygen in it than gas? I was thinking that if an air plane can use ethanol it must work better than gas at higher altitudes.

[EricTheCarGuy]

@switchgrassfuel That is a great question that to be honest I don't know the answer to. I do know that airplanes usually run a very high compression ration which is the reason they use such high octane gas but as for E85 or E50 I just don't know. Please post a comment if you do find the answer though because now you have me curious.

[switchgrassfuel]

@EricTheCarGuy Ok if i find the right answer i will post it. catch u later.

[EricTheCarGuy]

@switchgrassfuel Yea let me know what you find out as I'm curious now myself. Thanks for the really challenging comment.

[cuntsucks]

in a 1990 F-250, with a 351 windsor V8, what octane raing should i use?

[EricTheCarGuy]

@cuntsucks It probably just takes regular 87. Look on the dash on the speedo gauge and on the inside of the fuel door for something that says "Premium fuel only" if you see this then it takes premium, if it just says "Gasoline only" then you can just run regular in it.

[Rezikrisp]

I try telling people this all the time about octane ratings, they still insists that higher octane helps clean their engine or give them more power. I'm going to copy paste this video on facebook. Nice vid Eric.

[EricTheCarGuy]

@Rezikrisp I run into quite a bit of ignorance myself, no worries. Thanks for the post and the comment.

[TaLoCc]

@Rezikrisp there is only one way to find out.Dyno the car 91 octane against 100 and see if you would gain hp because im curious.

[Bobman84]

@Rezikrisp

Additives help clean the engine, but higher octane will always help if you get detonation on the lower grades of fuel. We have 91, 95 and 98 here in Australia and I'll always get pinging from the 91 octane fuel. I suppose you can adjust timing in some cars to compensate. I have experienced more power from higher octane fuel because the engine advances timing automatically when a higher grade fuel is used. Am I wrong though?

[elemineseslapolla]

this is awesome, i want to work in mechanics and want to have your experience some day, great explanation erictheprocarguy hehe

[EricTheCarGuy]

@elemineseslapolla Thanks for the commetn. Just remember that I was just like you once but after years of hard work and experience here I am. In other words, I know you can and will not only match my skills but perhaps exceed them. Good luck.

[jambe1234567]

nice video very informative. how do we leave comments/questions on your website pertaining to a particular vid?

thanks

[KenBobBad]

You should make another video explaining in more detail what happens with different octane ratings. Such as ignition timing with 87 and 93 at idle and under a load and how different ratings effect the amount of torque that can be produced.

[EricTheCarGuy]

Good idea but I don't think I could do that in 10min.

[KenBobBad]

Good point.

It took one of my old instructors about 45 mins to explain it, but he was also talking about cetane.

[ChowZeb]

Great Explination!

[EricTheCarGuy]

Thank you.

[Logarjoon]

Good job man!!! love it..

[timmitmit]

Dude, Love the video. Made it so simple to understand.

[EricTheCarGuy]

That was my intent, thanks for the comment.

[elicberry12345]

this is the best explanation I have seen so far! good job!

The other thing I was really surprised about engines when I realized that after burning fuel it produce lots of water and strictly talking it expansion cycle is mostly due to the water formation and it sound strange like it is running on water :)

[EricTheCarGuy]

Alchemy, it's cool.

[rick62008]

I really liked this explanation. I'll favorite it so that others that come into my channel will have a chance to see it too.

Good job.

[EricTheCarGuy]

Thank you!

[amvasierra]

shell v power racing all the way lol

[valleystylez]

fuck shell. It's Chevron all day. Lol.

[trdccm]

Thanks Eric. That is very clear and simple to understand for the man on the street.

[EricTheCarGuy]

That was my goal, thanks for the comment.

[1969MustangMACH1]

That was really good

[EricTheCarGuy]

Thanks man.

[1969MustangMACH1]

Finally a mechanic with all of the knowlage and experience, but has computer and editing skills and the drive to help others learn by putting it on camera. Really good thing you have going.

[EricTheCarGuy]

Well you hit it there man. That is exactly the direction that I am headed, I only hope that people are willing to buy it.

[1969MustangMACH1]

Yeah we buy it haha....I just wish you had a little more exposure ya know.

[EricTheCarGuy]

Yea, me too. I'm working on it. Remember that ETCG just began at the end of January as kind of a "let's try this and see what happens". If you have any ideas about getting more exposure I'm all ears.

[cland45]

As always, good job on the video!

[007mangoman]

Awesome video, my dad tried to explain it to me once but I didn't quite get it, the animation really made it make sense. Thank you

[cputb1]

Great explaination!

[EricTheCarGuy]

Thank you!

[EricTheCarGuy]

I try a little bit with each new video, thanks for noticing.

[bigblockmustang]

Try again..

Higher Octain fuel (MTBE) VS Ethanol

Ethanol altough a higher octain actually lowers the combustion chamber temp and lessen Hp due to BTU loss.. this will effectivly lower your miles per gallon..

Les

[EricTheCarGuy]

I tried to stress that this was about gasoline and deliberately stayed away from mentioning Ethanol, Diesel, or 2 stroke engines for that matter. It is a balance between giving useful information and too much information. As a result of your comment I'm sending you to the advanced class.

[bigblockmustang]

Ya, I messed up my first comment and had to re-do it. I was just hoping to generate some intrest in different fuels and get your comments section pumped up.. Hope ya didn't mind..

Les

[EricTheCarGuy]

Comments are always welcome, good or bad. The point is to find the truth in the end, if not, a difference of opinion will do.

BTW, I love your comments.

[bowlingballout]

Eric

That was very cool. In 2006 I was trying to go through a mechanics video course from Sea Doo. It started out with the combustion engine and the difference between a 2 and a 4 stroke engine. Also I learned about Octane. Just like you said, it isn't a "hotter" fuel like one would think. Makes me laugh to think of the guys that suggest putting "super" in the tank of a car it wasn't designed for... like it was going to get a few more RPMs out of it or something. :D

[EricTheCarGuy]

That's the reason I made the video, to try and set the record straight. I do get the question a lot about what gas should I be putting in my car? In my experience however people that have an opinion about something car related are seldom going to listen to other opinions. That's not going to stop me from making my videos though. Thanks for watching.

[BigLoveZone]

Always well done, Eric!

[EricTheCarGuy]

Thanks groovy movie maker!

[GenericGene]

Excellent presentation Eric and I learnt a lot, thank you - Gene

[EricTheCarGuy]

Thanks Gene.