What type of fuel are you using?

[matthew1]

... mainly city driving.

That's it. Stop right there. If we're talking city, mpg ranges are very wide. Huge. Why? Cities differ, mostly. I know streets and times of day in the city where I can get 22-24. But my city mpg is usually a combined 18 mpg or so. Volvo high pressure turbos are notoriously inefficient at stop n go driving while low pressure turbos and N/A engines are better.

In Seattle I got lower city mpg than Denver, because it was very very hilly. I know one 5-way stopsign intersection on Queen Anne Hill where you'd start at an 7-degree incline after inching up to your turn, then proceed turning left at an almost 180 degree turn, continuing uphill. Brutal on mpg. That 100-yard/meter scenario probably clocked in at 4 mpg.

So where am I going with this... here's where: the only common denominator for mpg we have is highway. Even that isn't perfect, average speed and passing being the biggest variables there. But it's the best common denominator we've got.

SO, get out on the highway, start your trip computer after you've gotten up to speed, and go 10 miles one direction and then 10 miles back, at least. If you can travel at 65 or 70 mph, that would be a further step toward "normalizing" your results so that we can begin to compare apples to apples.

I've found my trip computer to be very accurate, so you might want to check it before reporting highway mpg based on its readings.

[polskamafia mjl]

+Infinity, Matt. Even on my NA 850 my city MPG are terrible. 15mpg sounds about right for city. I like your idea, Matt, for comparing apples to apples. We could all submit our numbers and then see what the averages are.

[vegasjetta]

I don't have the trip computer, I am going by the old fill gas, run down, refill, calculate mileage.

I just changed the spark plugs and found what I would imagine are either original, or old replacement stock plugs. Here is a picture of them, as removed from the motor left to right:

IMG_2895.jpg (168.26 KiB) Viewed 1808 times

They all had the same amount of wear like this:

IMG_2902.jpg (185.25 KiB) Viewed 1808 times

Also, I noticed sludge built up on the oil dipstick and under the cap, I am hoping the seafoam will take care of that, if not I may have to do some kind of sludge flush. What do you guys recommend for that? I know with the VW's I play with, there are certain things you do NOT want to do...

And here is a pic for good measure:

IMG_2894.jpg (319.1 KiB) Viewed 1808 times

[jblackburn]

Those don't look terribly bad, you've still got a healthy engine!

As far as the sludge buildup, many people reccomend Seafoam for a total engine cleaning. 1/3 of a can in the gas tank, 1/3 in the oil, and 1/3 sucked into the intake manifold. Then change the oil within 200 miles or a few days of doing it.

I noticed my oil was jet black after I ran it through - usually it's still a dark brown. So it must have cleaned out something pretty good.

I'm not sure if you use synthetic in your other cars, but these engines love the stuff. My car became undeniably smoother and more free-revving after I switched to synthetic oil, and while it's expensive, I would never use anything else on it now

While you're at it, check the PCV system - pull out the oil dipstick on a warm engine with it still running and look for smoke puffing out of the opening.

[vegasjetta]

Those don't look terribly bad, you've still got a healthy engine!

As far as the sludge buildup, many people reccomend Seafoam for a total engine cleaning. 1/3 of a can in the gas tank, 1/3 in the oil, and 1/3 sucked into the intake manifold. Then change the oil within 200 miles or a few days of doing it.


I'm not sure if you use synthetic in your other cars, but these engines love the stuff. My car became undeniably smoother and more free-revving after I switched to synthetic oil, and while it's expensive, I would never use anything else on it now

While you're at it, check the PCV system - pull out the oil dipstick on a warm engine with it still running and look for smoke puffing out of the opening.

I will do the seafoam tomorrow sometime when I go down to the shop to check the brakes. I have been using that stuff for years, it's great!
I will go do the PCV check now. If it's puffing smoke, what will I have to clean out?
As for synthetic, cost is not an issue, as I get whatever Amsoil makes for free from my brother in law that is sponsored
Problem is, synthetic cleans stuff out and leaks past seals that were plugged up by gunk and regular oil couldn't leak past.

[polskamafia mjl]

If you get smoke and or positive pressure at the dip stick you need to replace your PCV system. Common repair on the Volvo 5 cyl engines...kind of boring and long but not difficult.

[Warren561]

the volvo manual calls for a minimum of aki 87 octane but recomends aki octane of 91 or over (anti knock index)says optimum pertformance as per their design is achieved with aki of 91 and over,,,

aki 87 = ron 91

this is straight from the 1995 manual.... the choice should not be that hard

Correct. Here's the excerpt from the 1998 S70 & V70 owner's manual.

Octane Rating

Volvo engines are designed for optimum performance on unleaded premium gasoline with an octane rating. AKI of 91, or above. AKI (ANTI KNOCK INDEX) is an average of the Research Octane Number, RON, and the Motor Octane Number, MON, (RON + MON/ 2).
The minimum octane requirement is AKI 87 (RON 91).

Link here: http://new.volvocars.com/ownersdocs/199 ... 5.htm#pg65

Note that "The minimum octane requirement is AKI 87 (RON 91)."
In the USA, most gas pumps (99.9%) list the octane ratings as (R+M)/2).

AKI is equivalent to (R+M)/2)
See: http://en.wikipedia.org/wiki/Octane_rat ... _.28AKI.29

Therefore, according the owner's manual the minimum octane requirement for our cars is 87 as measured by the (R+M)/2) method.

The various sensors on the engine "adjust" the combustion as necessary in order to provide the power requested based on the octane of fuel used. As the fuel quality changes, the settings are adjusted (over a certain moving average). Therefore, constantly running 87 then switching to 92 won't show an immediate improvement (over just one tankful).

Now, given the discussion about engine damaged due to running "non-premium" grade fuels, I believe that it is true, IF, you're frequently pushing your engine to its maximum design limits. Let's say you're running 87, and you're constantly pushing the redline or running 90mph for sustained periods (up down hills, etc...). You're probably going to cause the "adjustments" to start "adjusting" to their maximum (or minimum) settings in order to provide the power you need. At some point, you'll be asking for a setting beyond the capability of adjustment, and that's when you'll probably start to do some damage.

I've run 87 (AKI) since around 2006 (about the last 50,000 miles), mostly Shell or Mobil. Previously, I'd run 92 (AKI), mostly COSTCO gas. No damage yet (knock on wood). But then again, I don't have a turbo. And, 95% of the time I never "rev" over 3500 (even accelerating).

[nightc1]

I've owned 3 Volvo's all were run with regular grade (87 I believe). The 90' 240 DL was traded in with around 220K Miles and was still running fine without any major mechanical issue. My old 94' 940 was traded in when it had around 230K but it had some issue I didn't figure out. I should have kept the car, bought a code reader, and fixed it... but the leather was really getting bad, someone had backed into one of the front fenders :_| , and I wasn't prepared to spend the $$$$ to really bring it back to being a great car. Currently I just have the 99' V70 and other than my front 02 sensor going out (at ~150K Miles... which it was due 50K miles ago!) and the ABS Module issue that most everyone has... It's been a solid car. This is mainly used for my long commute to work.

In the V70... my trip computer says I get around 30mpg on 87 octane . I think the trick here is just making sure to clear the computer out by disconnecting the battery for a while (I usually just let it sit for a weekend, so I don't time it or anything) so it can optimize itself... maybe once a year or every other year or so.


EDIT:

And I mainly purchase all my fuel at the same Shell station.

[geokilla]

Hm back to regular I go I guess. Rarely does the engine rev past 3000 RPM. I'll discuss this with my mom and see what she wants to do. And she's constantly thinking of buying a Hyundai Sonata, so there's no point in running Ultra 94 if she's going to purchase a new car soon.

[polskamafia mjl]

Put good in, get good out.