Hello!

I am a new volvo owner -- just got 2003 XC70. Very happy with it so far.

The manual recommends 91 octane. That's what I intend to use. I mostly use BP (because I have their card), but their premium octane is 93. Now I feel like I'm overdoing it by two points. I tried to find some comparison charts of what other companies' grades are, but for some reason, this info is hard to find.

So my questions is: what are your favorite companies to buy your 91 octane gas?

Thank you!

 

I little secret about gas...

It all comes from your local refinery, with very few exceptions. (Locally we have Holiday stations with "Blue planet" gasoline and it's garbage.)

The difference in gasoline brands is the very small percentage of additives mixed in before delivery. Typically, additives are only used in premium grades, mid grade is a 50/50 mix of regular and premium and regular has no additives. (There are some exceptions)

Additionally, some places require gasoline to be oxygenated with ethanol. My state requires 10% ethanol. However, "classic" cars that do not run well on ethanol are allowed to use non oxygenated premium gasoline. Verification that your car fits the criteria of a "classic car" is left to (usually) a teenage kid making minimum wage, poorly trained and/or ignorant of the law.

Bottom line... I get the best gas mileage and performance from non oxygenated gasoline. My only choice for that is premium and BP is the most consistent dispenser of it in my area. Sometimes I will find a Shell station that offers it too.

Legally... I'm breaking the law by pumping said gas into my car. I would probably also fail emissions testing (if my state still required them.) Check what's legal and available in your area.

 

Thank you Dead_Eric, very interesting info!

I've never seen anything like "non oxygenated gasoline". Maybe I just don't know where to look. But again why would I need it... It looks like here, in Chicago area, all gas is with ethanol.

But excuse me being dumb, what about those darn octane numbers: 91, 92, 93...? Would it be that 93 is more expensive than 91? So my logic is: why would I pay for 93, if I need only 91? I guess that was my initial question. Or is it a wrong kind of question all together?

Thank you.

 

You actually only need 87.

 

It's kinda hard to explain in a sentence or two without assuming you know how combustion works. I'll try to keep it short and skip some of the extra stuff...

During the compression stroke, the air/fuel mix is compressed for better ignition. During compression the air/fuel mix is heated (by the compression alone) but is ignited by the spark plug. Cars that use a high compression ratio and use turbo (compressed and there for hotter air) to produce more power can run into detonation. Detonation is when the air/fuel mix is ignited from the heat of compression and not by the spark plug. Often before the piston has reached the top of the stroke. The exploding gasoline pushes down on the piston while it's still traveling up and cause damage to the engine. It also makes an audible sound often called a knock or ping.

The octane rating is a number give to the gasoline's resistance to detonation. The higher the number the grater the resistance.

Note the following 2 things...

1) Car companies tend to play it safe because consumers want long life from a car. The octane recommendation is not the minimum your car needs for all operations but it can sometimes have a need for that rating.

2) Gas pump octane ratings are a minimum rating that will come from the pump. As in, 87 can be 90 (or higher) but not lower than 87.

I myself stay mostly in a 5-10 mile radius (no highway driving) drive like an old lady and use regular gas. When I head up to the cabin I drive like I'm in Mad Max and try to make the 3 hour drive in 2 hours... then I get premium.

 

Thank you, Dead_Eric, very much for your great explanation! It all makes sense now, contrary to what I used to think before.

Interestingly, with this car I started driving in a city "like an old lady", with people constantly nervously tailgating me. This never happens when I drive my 99 4runner (which I'm selling now). And it absolutely never happens when I drive my 01 Dodge Ram pickup with a busted and rusted rear corner (who knows who drives that piece of junk...

 

My understanding is that you want to use gasoline with the best combination of additives, which not only prevent the detonation problem described above, but also help to prevent carbon buildup that clogs fuel injectors and interferes with proper functioning of valves, etc.

I suggest you google "top tier gasoline". To qualify and get certified as a top tier gasoline, it has to meet stated standards for the inclusion of additives. I know that two of the largest gasoline producers of top tier gasoline are Shell and Chevron. There are no Chevron stations in my area. You should be able to use regular gasoline from these producers knowing that it has met a certain standard for the inclusion of additives.

I myself use Shell 91 octane, and throw in a can of Liqui Moly Jectron every once in a while, followed by a can of Liqui Moly Valve Clean on the next fill up. You can find an abundance of similar products for sale at your local auto parts store. Shop around for the lowest price on 91 octane. In my rural area, Shell 91 varies in price from 23 cents to 54 cents above regular. Because a lot of the luxury high performance cars now require 91 or above, some gas stations are price gouging and taking advantage of this because to the increase in demand.

 

Well said, waydowneast! Thank you! We have Shell near us, I should check prices. So you think even with top tier detergent additives you still need to add some other products?

 

just checked this site: Retailers
it looks like all of them sell top tier gas now.

 

You don't need any additives. Direct injection engines require 91 octane and might benefit from those additives. You can easily just run 87.

 

adding more commentary - the ignition/fuel delivery system is controlled by ECU which gets information from the knock sensors. So, if you put 87 in say Volvo 850T - which I've been doing for 200K miles, the ECU will detect any ignition by compression (aka ping, pinking or knock - choose your vernacular) the timing and mixture is adjusted to cool the burn. The only time this comes into play is during hard acceleration or when you are pulling a large load so for the most part, running 93 is money out the window. To the earlier comment about oxygenated fuel - in the north we get the bonus of "winter blend" which is when the refiners add in extra alcohol or esters to reduce the COs and soot. MTBE used to be the common additive, but due to issues with leaky holding tanks and the fact MTBE doesn't break down in the water supply, the Govt mandated ethanol for oxygenation.

 

May I ask where you get this piece of information from?

 

Here is some text I copied from carfax site about their gas:

A 2000 Impala automobile with 3.8 V-6 engine was the test vehicle. The dual fuel test compared the deposit buildup performance on the intake valves using Shell V-Power’s additive package vs. an industry generic additive package for 5000 miles. The test started with new, clean intake valves.

The same premium octane conventional base gasoline was used for the test, only the additive packages differed. With the generic additive package, results demonstrated the average valve deposit weight increase was more than 200 milligrams while there was no increase in the deposit weight with the Shell V-Power additive package.

 

I could run mine on 87 from Sunoco, but I personally choose non-ethanol 91 when I can find it. (Locally Sunoco). It is more expensive and is probably not worth it but my mpg goes from 23 to 27. I don't get the same mpg boost from higher octane ethanol based fuel.

I assume that the engine runs better with non-ethanol gas so it must be better overall.
I only run non-ethanol in my boat and lawn mowers too.

 

i was under the impression that the turbo motors needed 91? maybe just the older turbo models?

 

Higher Octane are for high performance cars, if I can get away with low Octane gas I'll used it, my other car said 93 Octane fuel I tried 87 and Check Engine light came on, until I used 93 then the light is gone. I used 87 in this my 07 XC70 since I bought it ran fine so far. Don't waste money on higher Octane if you don't have to.

 

My car is a non-turbo inline 6. I am averaging around 25-26 mpg on non-ethanol 91. The car reverts back to 21 mpg on any ethanol-based fuel regardless of octane.

I agree that running the 87 is cheaper and just fine. I would run 87 too if I could find it in a non-ethanol version.

So do I go for 300K?

Cheers!