what is the best gas?

[CPanther95]

That's not what he said. They're required to be able to run on regular without damage. That the manufacturer refers to it as "premium required" is another matter. The specs themselves refer to "recommended fuel". I found the owners manual for the first car on the list:

http://owners.acura.com/vehicles/information/2016/MDX/specs#mid^YD3H2GJNW
http://techinfo.honda.com/rjanisis/pubs/QS/AH/BZ51616OG/enu/BZ51616OG.pdf

It's on page 114:

Use of unleaded premium gasoline of 91 octane or higher is recommended. ​

I had a 2007 Acura MDX that was marked on the fuel door:

USE PREMIUM UNLEADED FUEL ONLY
*SEE OWNER'S MANUAL

It didn't say "suggested" or "recommended" so it appears to be mandatory. The fact of the matter was that the only benefit to using premium fuel in the MDX was a boost of 5 HP. There was no other benefit. The reason they made it a Premium Fuel vehicle was because that extra 5 HP bumped it from 295HP to 300 HP and they wanted to be able to market it as a 300 HP vehicle.


As far as the best gas, it's the cheapest gas available that doesn't cause engine knocking with the least amount of ethanol you can get. Ethanol gives you something like 25% - 30% worse MPG than standard gasoline. Ethanol is more costly to make and performs much worse than gasoline.

If the Iowa caucus wasn't such an important part of the Presidential election process, we wouldn't be putting ethanol in our gas.

 

[tvguy]

I had a 2007 Acura MDX that was marked on the fuel door:

USE PREMIUM UNLEADED FUEL ONLY
*SEE OWNER'S MANUAL

It didn't say "suggested" or "recommended" so it appears to be mandatory. The fact of the matter was that the only benefit to using premium fuel in the MDX was a boost of 5 HP. There was no other benefit. The reason they made it a Premium Fuel vehicle was because that extra 5 HP bumped it from 295HP to 300 HP and they wanted to be able to market it as a 300 HP vehicle.


.

This kind of sums up my view.
http://www.cartalk.com/content/premium-vs-regular-1

 

[longboard55]

Foreign cars will often need premium. A salesman told me once that america makes cars for rentals and they assume only regular will be used. I think you can mess up the computer settings if you switch back and forth

 

[IndyRnRfan]

Some vehicles do Require high octane fuel. The reason being, it comes with a high compression engine. Typically, anything over 10-1 compression ratio will need higher octane fuel or a boosted engine running a higher boost rating then stock. Running higher octane doesn't increase horsepower but running lower octane can reduce horsepower if is recommended to run higher octane if that makes since.

 

[bcla]

I had a 2007 Acura MDX that was marked on the fuel door:

USE PREMIUM UNLEADED FUEL ONLY
*SEE OWNER'S MANUAL

It didn't say "suggested" or "recommended" so it appears to be mandatory. The fact of the matter was that the only benefit to using premium fuel in the MDX was a boost of 5 HP. There was no other benefit. The reason they made it a Premium Fuel vehicle was because that extra 5 HP bumped it from 295HP to 300 HP and they wanted to be able to market it as a 300 HP vehicle.


As far as the best gas, it's the cheapest gas available that doesn't cause engine knocking with the least amount of ethanol you can get. Ethanol gives you something like 25% - 30% worse MPG than standard gasoline. Ethanol is more costly to make and performs much worse than gasoline.

If the Iowa caucus wasn't such an important part of the Presidential election process, we wouldn't be putting ethanol in our gas.

The manual says 87 can be used temporarily. The warnings of engine damage seem to be more a CYA thing than anything. There's bound to be a knock sensor and a means to retard timing.

http://techinfo.honda.com/rjanisis/pubs/OM/AH/BTX0707OM/enu/TX0707OM.pdf

Fuel Recommendation
Your vehicle is designed to operate on premium unleaded gasoline with a pump octane of 91 or higher. If this octane grade is unavailable, regular unleaded gasoline with a pump octane of 87 or higher may be used temporarily. The use of regular unleaded gasoline can cause metallic knocking noises in the engine and will result in decreased engine performance. The long-term use of regular-grade gasoline can lead to engine damage.
​

As far as ethanol goes, it does serve a certain purpose. In much of the country there is a high demand for higher octane fuel, and without ethanol as an octane booster there's going to be a shortage of high octane fuel or other effects. It's certainly possible to make high octane fuel without ethanol, but if you understand how refinery streams work, the object is to use up everything to make salable fuel.

Ethanol itself has about 2/3 the energy content of gasoline. So at 10% it might result in a decrease of 3% fuel economy, which is highly dependent on energy content. Additionally, there's a lot of variation in the energy content of gasoline itself depending on the blend and the source crude oil - more than from using ethanol. Also - ethanol costs less than gasoline. Current futures prices are about $1.40/gallon. Back when gasoline was going for near $4/gallon, the amount of ethanol was easily bringing the price of pump gas down.

 

[bcla]

Some vehicles do Require high octane fuel. The reason being, it comes with a high compression engine. Typically, anything over 10-1 compression ratio will need higher octane fuel or a boosted engine running a higher boost rating then stock. Running higher octane doesn't increase horsepower but running lower octane can reduce horsepower if is recommended to run higher octane if that makes since.

Require is such a strong word. I know it says that on the filler cap doors of the last two cars I've owned, but then the owners manual says regular will still work with reduced performance.

I do understand that there are some exceptions, such as exotic cars where the engine puts out 500+ HP. They may even say that 93 octane is required, and that's a little hard to find around where I live, although I have seen it.

 

[xlxo]

I agree with the earlier comment about checking what's in the owner manual. If the car says to use 87.... get 87. If you have a knocking problem... then pay a little more.

Now the question who makes the best gas..... brand vs no-name. Does that local station have a leaking tank with water contamination? Costco? Try to stick to one brand. If you frequently mix brands.... the formulas (detergents) can cause problems.
https://en.wikipedia.org/wiki/Shell_Canada_lawsuit

Check out this vid if you want to experiment with diesel misfuelings....
http://losangeles.cbslocal.com/2016...s-costing-some-customers-hundreds-of-dollars/

 

[bcla]

I agree with the earlier comment about checking what's in the owner manual. If the car says to use 87.... get 87. If you have a knocking problem... then pay a little more.

Now the question who makes the best gas..... brand vs no-name. Does that local station have a leaking tank with water contamination? Costco? Try to stick to one brand. If you frequently mix brands.... the formulas (detergents) can cause problems.
https://en.wikipedia.org/wiki/Shell_Canada_lawsuit

I've never heard of any specific issue with mixing detergents. Mixing base fuels is done all the time, even with the same name on the pump. I also looked up the Shell Canada issue, and that was a specific incompatibility between the additive, the base fuel, and the fuel system. It had nothing to do with mixing brands.

http://www.theglobeandmail.com/report-on-business/shell-apologizes-for-fuel-foul-up/article25692540/

Some brands even have different detergent formulas they use in different seasons, and some don't even use anything but a generic additive that's available at the fuel depot.

 

[IndyRnRfan]

Require is such a strong word. I know it says that on the filler cap doors of the last two cars I've owned, but then the owners manual says regular will still work with reduced performance.

I do understand that there are some exceptions, such as exotic cars where the engine puts out 500+ HP. They may even say that 93 octane is required, and that's a little hard to find around where I live, although I have seen it.

Oh, I agree. Always go with the owners manual, of course that means people would have to read it and most don't. My wife's Pontiac says Mobil 1 synthetic on the oil filler cap. You'd be surprised how many people on the Pontiac forum think you can only use Mobil 1 oil. The owners manual states any synthetic that meets GM ####. I can't remember the 4 digit number. I know auto manufacturers vary on this but I'm not 100% sure on how much timing they allow the computer to retard but in the example of the Acura mentioned a few posts before Acura had that thing bumped up to 11 or 11.5 to 1 compression which doesn't make since to me. You might be able to run 89 in that during the cooler months but definitely not 87 unless that computer can pull a lot of timing.

 

[Gumbo4x4]

Some vehicles do Require high octane fuel. The reason being, it comes with a high compression engine. Typically, anything over 10-1 compression ratio will need higher octane fuel or a boosted engine running a higher boost rating then stock. Running higher octane doesn't increase horsepower but running lower octane can reduce horsepower if is recommended to run higher octane if that makes since.

I remember in the old days anything over 9:1 and you'd better be thinking about premium. Nowadays, it's not much of an issue until 11:1.

 

[Shutterbug]

No it doesn't. It requires certain cleaner burning fuels which are usually achieved by additives to regular gas. The Acura RDX and every model of mini cooper require premium. Not recommend but require.

Yep my Subaru requires premium as well

 

[Shutterbug]

Now as far as quality of the gas:
http://www.toptiergas.com
and
http://www.toptiergas.com/retailers/

 

[IndyRnRfan]

I remember in the old days anything over 9:1 and you'd better be thinking about premium. Nowadays, it's not much of an issue until 11:1.

Was this back in the leaded gas days as they were switching over to unleaded?

 

[Squirlz]

All 4 of our cars "require" premium. Three of them are supercharged. I use 93 octane from Meijer. On our car forums there is always "that guy" who says 'Why waste your money on premium when it runs fine or regular?' Well, it doesn't. It hampers performance and mileage. Not worth any savings at all.

I put premium in my snowblower as well. The main reason for that is so I can empty the gas can into one of the cars in the Spring so the gas doesn't sit around.

 

[IndyRnRfan]

Now as far as quality of the gas:
http://www.toptiergas.com
and
http://www.toptiergas.com/retailers/

I always try and buy from top tier stations. This and change the oil and filter when you are suppose to. It makes a big difference on how your engine operates and looks on the inside.

 

[CPanther95]

All 4 of our cars "require" premium. Three of them are supercharged. I use 93 octane from Meijer. On our car forums there is always "that guy" who says 'Why waste your money on premium when it runs fine or regular?' Well, it doesn't. It hampers performance and mileage. Not worth any savings at all.

I put premium in my snowblower as well. The main reason for that is so I can empty the gas can into one of the cars in the Spring so the gas doesn't sit around.

I replaced my MDX with a 2010 Camaro SS. It would run on lower octane gas, but anything under 93 or 94 octane and the computer completely changed the settings of the [some "car guy" can insert whatever it is here] that made a fairly dramatic change in performance (not that I needed all 426 HP, but I liked knowing it was there )

Unfortunately a flaw in the software prevented it from changing back and forth as it sensed the different octane levels. Once it switched "down", it would never switch back without pulling a fuse overnight and resetting the system.

 

[bcla]

I remember in the old days anything over 9:1 and you'd better be thinking about premium. Nowadays, it's not much of an issue until 11:1.

A car I owned a while back had an engine with a 10:1 compression ratio and the back of the filler cap door said "PREMIUM UNLEADED REQUIRED". Of course the owner's manual said that 87 octane would work with reduced performance and fuel economy. It was naturally aspirated too.

It's a lot more than just compression ratios. There's how aggressive the timing is, along with forced induction. It's really about what kind of pressure is reached when the fuel-air mixture compresses, and that pressure can be higher with a higher compression ratio and/or forced induction. An engine with an 8:0 compression ratio and 11 PSI of boost is going to need premium to operate without sucking away some of the performance.

 

[bcla]

Now as far as quality of the gas:
http://www.toptiergas.com
and
http://www.toptiergas.com/retailers/

Top Tier says nothing about the quality of the fuel per se. Their requirements are strictly about the detergent additive and its ability to control fuel system deposits. The fuel itself is a commodity. The brand of the pump isn't likely to be the same as the refinery. Heck - I recently noticed a Sinclair branded station near where I live, and there isn't a Sinclair refinery within 1000 miles of here. And those refineries probably aren't producing California reformulated gas.

 

[Shutterbug]

All 4 of our cars "require" premium. Three of them are supercharged. I use 93 octane from Meijer. On our car forums there is always "that guy" who says 'Why waste your money on premium when it runs fine or regular?' Well, it doesn't. It hampers performance and mileage. Not worth any savings at all.

I put premium in my snowblower as well. The main reason for that is so I can empty the gas can into one of the cars in the Spring so the gas doesn't sit around.

Does the Morgan take Premium?

 

[Gumbo4x4]

A car I owned a while back had an engine with a 10:1 compression ratio and the back of the filler cap door said "PREMIUM UNLEADED REQUIRED". Of course the owner's manual said that 87 octane would work with reduced performance and fuel economy. It was naturally aspirated too.

It's a lot more than just compression ratios. There's how aggressive the timing is, along with forced induction. It's really about what kind of pressure is reached when the fuel-air mixture compresses, and that pressure can be higher with a higher compression ratio and/or forced induction. An engine with an 8:0 compression ratio and 11 PSI of boost is going to need premium to operate without sucking away some of the performance.

Well, if it's boosted, the effective CR is higher. Hence the reason you see lower CR in such applications.