Herman and Operation 30MPG

[oragex]

For non turbos the compression ratio is 11 to 1 on white blocks so this is well suited to low grade fuel.

During cooler months you can get away with a mid-grade fuel on turbos but nothing less if you want to avoid detonation.

+1

My non turbo does pretty neat with lower grade. I'm sure I loose a few mpg's but no detonation. However, I had a lot of pinging when the engine wasn't properly sorted (non OEM spark plugs, faulty intake air thermostat, also failed coolant thermostat).

Again the turbo has a different compression but for non turbo, if the engine is in good condition, there should be no pinging under heavy acceleration with 87 gas.

[callahanoffroad]

Oh wow! Lots of replies!
Let me try to address these to the best of my ability.

The MAF (mass airflow sensor) was in fact dirty. Hence the cleaning. I foolishly put an inferior air intake filter in the car when I first purchased it. I was a little short on cash and couldn't find a Mann filter, so I grabbed a STP filter instead. Well the foam seal wasn't thick enough to seal the airbox properly and the snaps kept coming undone on the airbox. I honestly had way bigger issues to deal with so I never thought anything until the car didn't start... Saw dirt in the MAF screen and on the top of the air filter box and realized what happened. So now there is a nice clean Mann filter in the airbox again.

As far as resetting the ECU, I have a manual so I'm not sure how to reset the ECU again. I was under the impression that it relearned all on its own. I've put about 1000 miles on the car since I unhooked the battery last. That was about two weeks ago... Haha

As far as octane goes I may try a midgrade tank next week and see how it goes. I'll report with results. Midgrade locally is 89 octane.

As far as city vs highway driving goes my delivery area (radius) is in the western suburbs of St. Louis Missouri, so it's mostly long drives around 45mph (70kph) through semi-country roads. So I should be averaging higher than what I would get in a city center. We even have those lovely roundabouts! I actually really do love them.

I do have some good news to report though. I had a lot of running around to do on Sunday and I returned 25 mpg over half a tank. Looks like oil weight really does affect mpg. I'll have conclusive results tomorrow.

That fact about pressurized air being required is fascinating, makes me think that the "cold air intake mod" that expands the size of the intake tube coming from the stock location may have something to it.

I suspect that I have an exhaust leak somewhere, and to be honest the fact that the hangers are Rusty is none to reassuring either. I used to live in Texas and I had an exhaust fall off my truck. It was pretty hilarious actually.

That brings me to the O2 sensors. I haven't found any records that suggest that they were ever changed. I'm at about 186,xxx miles presently. I was thinking about replacing the whole exhaust system and the O2 sensors at the same time. I believe the service interval on those are 100,000 miles. So if they were properly serviced like it seems most of car was they'll be due in about 20,000 miles.

Does anyone know the overhaul schedule for these engines? Is it better to overhaul an engine or swap in a lower mileage unit from a junkyard?

Thanks for all your help everyone! Can't believe how international this forum is! ;-D

[June]

I have never heard of a overhaul schedule for a Volvo engine. I can tell you the dealer installs new unused engines if one blows. My 850 2.3 locked before it was one year old and Volvo put a new replacement in (warranty) though I had traded it while it was being fixed for a new 960. For fun I asked what a new T6 engine installed in my 2004 S80 would cost me and was quoted $12,000.00 and readily available.

I have never replaced a oxygen sensor in any car. I looked at my 2004 maintenance schedule and see no replacement interval listed. You may want to check the book to your car unless they are bad. So glad all is well! June

[Rattnalle]

Dealers here will get used engines as well if they can get them. But no there's no overhaul schedule. They will do 500 000 km or more in police cars and taxis with just regular service.

AFAIK there's no interval for the O2 sensors either. Sure they can break but it's a replace as needed part.

For mostly longer drives at 70 kph in fifth my 854 would do just above 7 liters/100 km.

[callahanoffroad]

Dealers here will get used engines as well if they can get them. But no there's no overhaul schedule. They will do 500 000 km or more in police cars and taxis with just regular service.

AFAIK there's no interval for the O2 sensors either. Sure they can break but it's a replace as needed part.

For mostly longer drives at 70 kph in fifth my 854 would do just above 7 liters/100 km.

That's about 33 us miles/gallon which is about what I used to get on long highway drives across Kansas in my old wagon.

[abscate]

Robert Bosch recommends replacement of second generation heated OXS every 100k miles. They usually fail sluggish, rich running, but they can fail lean which can wipe out your engine.

I replace mine in the 100-120k range.

[wizechatmgr]

Someone should make a DSP/A-D/D-A that plugs in in-line (a violation of EPA/CARB/you name it) that causes it to fail/indicate beyond rich (out of bounds) after X number of minutes showing lean. That should trigger an OBD code I'd hope.

*Starts staring at an Arduino shield sitting on his desk unused with a dirty look and a frown*

[FLXC90]

As far as resetting the ECU, I have a manual so I'm not sure how to reset the ECU again. I was under the impression that it relearned all on its own. I've put about 1000 miles on the car since I unhooked the battery last. That was about two weeks ago... Haha

That brings me to the O2 sensors. I haven't found any records that suggest that they were ever changed. I'm at about 186,xxx miles presently. I was thinking about replacing the whole exhaust system and the O2 sensors at the same time. I believe the service interval on those are 100,000 miles. So if they were properly serviced like it seems most of car was they'll be due in about 20,000 miles.

Does anyone know the overhaul schedule for these engines? Is it better to overhaul an engine or swap in a lower mileage unit from a junkyard?

Yeah forgot you have a stick

O2 sensors when they go far enough out will code. But they may be just within parameters, but less than peak efficiency.

Overhaul? What is this overhaul you speak of?! Compression/Leakdown would be the indicator for overhaul, probably just top-end. If you follow Robert's videos you'll know that these things just plain last if kept up.

[oragex]

That brings me to the O2 sensors. I haven't found any records that suggest that they were ever changed. I'm at about 186,xxx miles presently. I was thinking about replacing the whole exhaust system and the O2 sensors at the same time. I believe the service interval on those are 100,000 miles. So if they were properly serviced like it seems most of car was they'll be due in about 20,000 miles.

People don't replace the O2 sensors at an interval. Indeed, plenty of sites on internet say an O2 sensor don't last past 100K miles, but that just myths, perhaps from early cars with such sensors. Yet, an O2 sensor may fail because of poor engine combustion, so if an O2 failed, the engine issue must be fixed first or the new O2 sensor will also be damaged.

Also, from what I've seen, when the O2 fails it's mostly the city driving mpg that is affected, but I might be wrong.

[callahanoffroad]

Well, I have some seemingly positive results. After a week of work I've managed to verify that my average mpg over two tanks has gone up. Looks like 24 mpg is the new average. 10w-30 definitely made the biggest difference by far.

24 mpg is good, but I think I can find some more in there. Gotta squeeze out a few more mpg!!!

I have done all of my tests so far with 93 octane fuel (us premium). I am going to run a trank of regular (87) and midgrade (89) simply for posterity and to lend some much needed clarity to the octane question.

Once I have those measurements I hope to have a plan in place to begin squeezing out those extra mpgs. I will keep you all posted!