Canadian Chat → Re: Speed limits going up in BC

What about premium vs. regular gas?...I dunno I'm about to test a theory on my next tank, while my VW Manual says it can run fine on Regular gas, I find I get about 1.0L/100km worse fuel economy on my trips vs. premium (it basically works out to about an extra 100ish km per tank)...I know this may be specific to VW but I'm wondering why that is the case, I feel like my driving habits aren't any worse, but the rated fuel economy on my vehicle is 9.9L/100km City and 6.9L/100km Highway....but I tend to get about 6.3L/100km on the highway with premium and 7.3L/100km with regular.

Anyways . I am familiar with this physics because of our friend "Air resistance", damn you air!!

If the engine is designed to benefit from premium by sensing the fuel and adjusting things like the compression ratio you might get increased output which could potentially translate to better mileage, but other than that premium is just a waste unless your car specifically needs it.

it depends on your car, your engine, and the gas...there are a lot of variables involved.

modern cars have extensive engine control modules in them to detect knocking and pinging...using a fuel that is lower in octane rating than the recommended fuel, or using crappy fuel, will force the engine control module to make adjustments in order to compensate...these adjustments vary from air and fuel mixture, but mostly ignition timing...by retarding the timing, it will help reduce/prevent pre-ignition, but will also hinder performance...that means, instead of giving it X throttle, you need to give it X+1 throttle to compensate...the "it feels peppy" some people experience isn't that the engine is suddenly more powerful, it just means the engine isn't "cutting back" like it may have been before.

my Rio5, detests RCSS regular fuel, even though my car doesn't require or even recommend premium...likewise, it runs like a dream on Shell V-Power...i am trying to find a decent "regular" grade of fuel that doesn't contain ethanol that my car likes...sadly, the amount of non-ethanol "regular" fuels available is practically zilch...there is a Costco gas station opening soon here, so my hope is they will have better gas than RCSS...my assumption is the RCSS gas doesn't have any of the additional additives that qualify it as a "Top Tier" fuel...the cheap shit runs fine in the Hyundai though...i can only assume the higher compression of my Kia means the cheap stuff just isn't really good enough.

Compression ratio is static unless they have some new fangled technology. They adjust the timing. For every degree of advance you get an increase in power and mileage. It's a battle guys with supercharges and turbos fight all the time at the track.

yup, and the opposite is true as well...with RCSS gas, my car pings like crazy, and my fuel economy suffers...last tank was 8L/100 kms...current tank is sitting at 7.0 (V-Power), although only at half way, but will likely settle in that 7-7.2 number when empty...that last tank of RCSS gas is the last one i'll put in my car...i might break down and get some regular from wherever else, but i'd like to avoid ethanol if i can.

My CTS-V is supercharged so it needs premium fuel to run optimally. I suppose I could get away with regular in an emergency but I haven't had to do that yet. Presumably the computer will just retard the timing.

I think most modern vehicles would, or are at least better with the whole regular/premium fuel options.

My RX300 (from 2001) can only take premium, whereas my Veloster recommends 1 out of 5 tanks be premium. I usually go for premium because I get an extra 150k per tank, but it's nice to know that I'm not going to kill my catalytic converter over a tank of regular.

EQ

You know its funny, my car acted the same way with RCSS gas. There was a new station that opened up near my work and the gas was a bit cheaper so I thought why not try it out and get 2c/L in superbucks....

Yeah that's the last time my car went to RCSS....but my car does seem to be happier with Shell gas, right now I have a tank of Petro Can Premium in it and so far its working out about the same as the Shell premium gas, but I'll find out more in a few days when I get back to work.

I was thinking next time of going to Shell regular and see if my performance suffers.

Its hard to get a straight answer from the internet, I have the back sheep of VW engines the 2.slow engine non-turbo.

your car should be ok with any "regular" grade of quality fuel...my car would likely run fine on quality regular grade as well...i did fill it once with PetroCan regular and it was fine...as i said, my only preference is trying to avoid ethanol...sadly, it's in pretty much every regular grade blend.

Most modern cars are "smart" enough to know if they're being fed regular fuel and are able to adjust to handle it.

You're probably right. In reality I didn't realize there was such a thing as a "Tier 1" fuel vs. a Tier 2 fuel station....who knew.

they do, they retard the timing...but by retarding the timing, you still hear the pinging (as it is adjusting itself to compensate) and results in reduced power and fuel economy...the sound is akin to a couple of marbles jumping around in the cylinders (although, somewhat quietly)...it only does it when under load, so casual cruising on a highway likely won't produce it, but brisk acceleration, or even going up a small hill without forcing a downshift will load it up enough to cause it...as i said, our Hyundai runs fine on it, but my Kia doesn't...the Hyundai has regular fuel injection whereas my Kia has high compression and direct injection...it creates more power, provides more efficient combustion, and gets the CAT up to temp in 8 seconds vs 30-40, so it also is better for emissions...it's only downside is higher compression engines are more finicky about the fuel...as i said, i can likely use regular grade PetroCan, Shell, etc and it will be fine as those are all "Top Tier" fuels...i just prefer to avoid ethanol if i can...i may have to give in though, unless i want to keep using V-Power.

as i said, let your car tell you...our Hyundai works fine on the shit gas, so that's what we put in it...my Kia is too picky though.

My ram hemi gets consistently better fuel mileage at 110-115 on the highway than 100 or 120. And as for regular fuel economy with a mix of rural highway and city driving getting to work, I get approximately 75 kms more to a tank using 89 octane which the truck is rate for than 87 octane. The difference however is jumping to 91 or 94 octane is negligible or non existant over 89 octane. I definitely do notice it runs better without ethanol which unfortunately is only found in 91 and higher fuel and only at certain stations. The difference is even more noticeable with the dual exhaust system I have on my truck vs my old truck

I thought that ethanol was in fact required to be in the regular and mid level fuels "when available" in Ontario (up to 10% in regular gas and up to 5% in mid grade)

My car, even before I did the engine modifications that I did, always got Shell V-Power premium gas because the one time I ran it on regular grade Esso gas, it ran like a sack of s**t (and it was gas from a busy Esso station in Mississauga, so it was unlikely just a bad batch of gas)

NefCanuck

yea, i think it is kind of required/recommended, but there are a few stations who do offer ethanol free fuels...however, getting ethanol free regular gas is very difficult...there are a few places to get ethanol free premium blends though.

»pure-gas.org/