Gasoline for Turbo engine

When my wife got an US WRX we tried using 89oct to save money. The car learnt, she drove it easy, and we didn't have any problems. Yes you could tell it was a little down on power. But after doing this for a while and doing the math, it wasn't any cheaper because the car got worse MPG using the lower octane. We have found the higher the octane the higher the MPG. 92 = around 25mpg, 94 got her up in 27ish range.

89 she was down in the 23's on average.

She uses 92 now because it's our local gas station and her car has been modded & reflash with a 91 octane program. She's in the 25mpg range for daily driving and making around 270hp. :)

reccommended

Octane booster is a joke. Period. Toluene/Xylene are about the only products I would ever recommend to increase octane rating. The guy was worried about the cost of fuel, not the availability, you do realize that "octane boosters" only raise the octane (at most) .5 to .7 octane (thats what they mean by 5 to 7 points increase..".5"=5 points, ".7"=7points) ....it will take an awful lot of bottles to increase 87 octane to 91 or greater.

not to mention the heat penalty, ethanol burns hotter and doesn't have as much energy being produced when it burn as regular petro does.

Ragnar wrote in news:41f7cdd6$1_5@127.0.0.1:

That would be nice, but my choices are 87, 89, and 93 where I live. I suppose I could mix the 89 and 93 in 50-50 ratio.

Heh, it's not about whether I CAN afford it... it's just about whether I can save some $$$ on a long trip where the extra boost will hardly make any difference to my driving experience.

I'm starting to think the answer is no, unless I can find a way to temporarily (and reversibly) disconnect the Turbo.

y_p_w wrote in news:Gz%Jd.6662$ snipped-for-privacy@newsread3.news.pas.earthlink.net:

1) Wisconsin, USA. Will be travelling to other regions of the USA. 2) Baja Turbo

The Subaru manual implies the last. I wonder if that's just legal CYA.

My point exactly. That's the whole purpose behind the question. I'll be cruising at 75mph for long distances, so why waste the money if I don't have to?

Hmm... how often does this happen?

snipped-for-privacy@webtv.net (Vince C) wrote in news:2811-41FCE482-25@storefull-

3271.bay.webtv.net:

Was this mostly city driving?

Sorry - that's what threw me for a loop. I've never heard of 93 octane (R+M)/2 as a commonly-available "premium" unleaded. Where I live it's typically 87, 89, and 91 (used to be 92). If I bought a WRX STi (the only Subaru car at this time that NEEDS 93+ octane unleaded) I wouldn't know where to find the correct fuel.

As stated, your actual requirement is for 91 octane (R+M)/2 unleaded gasoline. More likely than not, a 50/50 mix of 93 and 89 octane should blend to something reasonably close to 91 octane, but there could be some strange effects where you might not hit your target.

Then you've probably got other problems (like cold weather) to deal with. If you're travelling, then you're not likely to find that 93 octane that's readily available.

91 (R+M)/2 octane requirement.

I think they're reliable enough that some manufacturers (like Toyota) are willing to risk that they won't fail during the warranty period. However, oxygen sensors fail. Plug wires fail. If it were my car, I wouldn't risk it.

75 cruising on flat land in 5th gear would probably mean a fairly light boost if at all. It won't knock. Going up hills will increase the likelihood, especially if you downshift. If you inadvertantly punch it, who knows what might happen? The big worry shouldn't be what happens most of the time, but what's your worst case scenario?

Like I said - I wouldn't personally risk it. At the very least, use a mid-grade (89). A single bad case of detonation could trash your engine and might not be covered under warranty. With the Toyota knock sensor, perhaps they use a less agressive system?

One thing to consider. My observations is that regardless of overall fuel price at the pump, the price difference between grades is typically 10 cents, although a few retailers differ. With higher overall prices premium is only marginally more expensive now.

One more thing to consider. Octane requirements at high altitude are typically reduced because of the thin air; pump octane is lower. If you're travelling through Denver or Salt Lake City, the fuel sold there may not be adequate once you get closer to sea level.

Well, my experience with my turbo Audi A4 is that my mileage drops if I don't use premium fuel, and I noticed this significantly when doing my 2x and 3x weekly 140-mile commutes from Rochester to Buffalo in Western New York. Premium fuel in a turbo engine matters even at cruising speeds. Sometimes to save $$ I would do a 50/50 mix of 89 and 93 (can't always find 91 where I am), and that would be ok, but it's a pain in the butt to do.

You could install a manual BOV that you can set the boost pressure. If you set the boost pressure at 1 or 2 PSI, you won't have to worry about detonation and you can use regular. However, my guess is that the cost of the BOV will exceed any savings you could hope to get by using regular, and because the engine is designed to be turbocharged, it has a lower compression ratio than a comparably-sized N/A engine; which means it will likely be gutless at any speed.

You might dial your boost controller to "show" 1 or 2 PSI, but it won't mean anything, since the wastegate spring pressure alone averages 7-8 PSI.

If you go below the mfr specs, you'll have to worry about detonation. "Pay now or pay later," there's smarter ways to save money.

The only thing worse than someone ignorant, is a know-it-all who won't share their 'knowledge'.

BTW it was a light hearted comment, get over it and switch to decaf.

Feel free to enlighten all us ignorant low-lifes if you can see it in your heart to type something worthy of reading........

I'm not angry. My "bullshit" comment was the all-purpose BS meter response.

I've posted it several times in this thread, but one more time won't hurt. I'm guessing part of his frustration is that the explanation has already been given.

Pump octane in Australia: RON, or Research Octane Number.

Pump octane in the US/Canada: (R+M)/2, also known as AKI (anti- Knock Index), which is the average of the RON and MON (Motor Octane Number).

In general, a US 87 (R+M)/2 octane "regular unleaded" fuel should be equivalent to 91 RON octane. A US 91 (R+M)/2 octane "premium unleaded" fuel should be equivalent to 96 RON octane.

"Technically there are three different "octane numbers" associated with every gasoline. The Research Octane Number, or RON, is measured under fairly easy test conditions. The Motor Octane Number, or MON, is a tougher test measured at higher engine speed and temperature.

The value that relates most closely to actual driving conditions is the average of these two values: Road Octane Number = (RON + MON)/2. This Road Octane value is the one referred to in Shell stations: Shell Bronze gasoline has an octane rating of 87, Shell Silver is 89 and Shell Optimax Gold is 91.

Occasionally, less scrupulous Canadian gasoline outlets will use the confusion of these different octane measurements to exaggerate their octane rating claims, by advertising their fuel's Research Octane Number - which will be higher than the Road Octane Number. It is also a common practice in many European countries to advertise the Research Octane Number on their pumps, so you may see unexpectedly high octane values when travelling abroad. In Canada, motorists should always be sure that the octane number a vendor advertises is its Road Octane value, not its RON."

I would love for you to show us evidence of that! In Canada, only the AKI may be published unless it is clearly marked as an RON octane number. It is OK not to put any octane numbers on the pump, but in all of my travels all across Canada, I have only ever seen an AKI number indicated on the pump for octane; they are 87, 89, 91, and 94.

advertise

Hey - I only pasted it from the Shell Canada website. That being said, they did couch it by saying that less scrupulous outlets advertise those exaggerated claims, but never said they do so at the pump. They specifically mentioned that RON is commonly advertised at European pumps (which seems to be the norm).

It was a frivolous untruth that was supposed to be funny but missed because of the ignorance on which it was based. You can bluff and bluster all you like but that's the truth.

D

It is the norm in Europe. However, any 'unscrupulous outlet' that did that in Canada and did not specifically note that it was RON and not AKI would find themselves in trouble with both the distributor and the BBB. So, I don't believe it at all and, having driven across Canada six times, I have never seen anything on the pump except AKI.