Really bad MPG since winter hit??

[JCL]

Originally Posted by omodos

Well i fill up at a local esso gas station, no idea how good the fuel is there, sorry for the wrong link, the one i used was the one for complete fuel system clean, injectors etc....

No problem with the link, when you look at the Redex product on the manufacturer's web site, they list all of the products (petrol, gasoline, system cleaner, injector cleaner, total cleaner) as having the same composition. It is still a solvent.

I have no idea how to judge diesel fuel quality in Cypress, but would ask a trusted local mechanic where they see there are fuel issues and where they see fewer fuel issues.

[racingbmwm3]

I agree that adding ethanol automatically reduces fuel consumption based on energy calculations. Non-ethanol combined with the higher octane would account for the increased mileage. I was wondering if the DME reprogramming that helped BMW's idle and run smoother after 10% became year round in the US, would need to be rolled back to the original version to get the most benefit from a non-oxygenated gas?

Top Tier Gasoline

Canada
Chevron Canada
Esso
Petro-Canada
Shell Canada

Top Tier site doesn't mention requiring 8% ethanol.
Also, TOP TIER gasoline can contain ethanol up to a maximum of 10% by volume. In areas where ethanol is not always used for blending, a TOP TIER gasoline that has passed all performance testing is still qualified as the additive supplier would have tested their product on the appropriate fuel.

[JCL]

The higher octane has zero impact on fuel mileage. No more energy content. And if the fuel has an AKI high enough not to retard timing, anything more is a waste. My best mileage ever in my E53 was on 89 AKI, not 91 or 94 (this was before ethanol contamination).

Originally Posted by from Top Tier Standard

1.3.1.2 Base Fuel.

The base fuel shall conform to ASTM D 4814 and shall contain commercial fuel grade ethanol conforming to ASTM D 4806. All gasoline blend stocks used to formulate the base fuel shall be representative of normal U.S. refinery operations and shall be derived from conversion units downstream of distillation. Butanes and pentanes are allowed for vapor pressure adjustment. The use of chemical streams is prohibited. The base fuel shall have the following specific properties after the addition of ethanol:

1.Contain enough denatured ethanol such that the actual ethanol content is no less than 8.0 and no more than 10.0 volume percent.

2.Contain no less than 8 volume percent olefins. At least 75% of the olefins shall be derived from FCC gasoline as defined by CARB (advisory letter, April 19, 2001).

3.Contain no less than 28 volume percent aromatics as measured by ASTM D 1319 or D 5580.

4.Contain no less than 24 mg/kg sulfur as measured by ASTM D 2622 or D 5453. At least 60% of the sulfur shall be derived from FCC blend stock.

5.Produce a 90% evaporation distillation temperature no less than 290F. as measured by ASTM D 86.

6.Produce IVD no less than 500 mg averaged over all intake valves.

Read more here:

Top Tier Gasoline

[racingbmwm3]

I'm not inclined to run less than 92 in our 4.6. Although, the SkyActiv family runs on 87 with 13:1 compression somehow...(91 minimum for the 14:1 engines)

Like I mentioned, I'll take a look at my intake valves and injectors next time I have the intake manifold off and determine if I should make the switch to Pacific Pride and supplement my own additives every tank...

[campy82]

I've known that using the heater has an impact on mpg, but recently read that using the seat warmers can also impact fuel consumption... Anybody vouch for that? if the fuel light is coming on after 250 miles, I'd start looking at the fuel system cause that's pretty low- even for all city driving..

[racingbmwm3]

would need to know the efficiency of the alternator, but let's say you have front and rear heated seats, each pulling 15amps at the high setting? ~200W/seat (@14V). ~800W total. If the alternator was 100% efficient, that is about 1.1HP. even assuming a horrible efficiency of the alternator of maybe 50%, that's 2HP. Same logic goes for the heater, but the heater has even less impact since the fan is the only (large) electrical load. The heater does have an impact on the length of time it takes to heat your engine up to operating temp though.
Which is the main reason for lower mileage in the winter. Longer warmup cycle, meaning the engine is running rich for a longer period of time. Combined with longer warmup times for the oil in the engine, transmission, transfer case, and front and rear differentials. That's alot of sources for increased drivetrain losses due to thicker fluids. Additionally, the cold air isn't ideal for a complete burn, but once warmed up, your O2 sensors account for this and correct it as much as possible.

[bcredliner]

My first thought was one of the two mileage calculations is incorrect or there are symptoms or codes indicating another cause such as the MAF or a vacuum leak or an O2 sensor. However, this winter is atypical so any outside conditions that are a negative impact on mileage are unusually high.

I think open 'cold' are systems are less effective but they may increase the amount of air getting to the engine. Since an engine is an air pump, more air combined with more fuel should result in some level of increased power. However, the engine must be able use more air than the stock system allows.

I think closed cold air systems are better but I have never read any third party tests for verification. I do notice that serious racers and shops that their income is based on verified performance measurements almost always include a cold air system in the most mild modification packages and the majority are closed air systems. The key there is that air box is part of other mods that need more air to be maximized.

If your engine is not modified and it can't use any more air the only positive result of an any aftermarket air system will be looks and you can hear the air going into the engine better.

The engine increases fuel because the engine is not up to an efficient operating range and cold air is more dense. The colder the weather the longer it takes to reach optimum engine temp. Your system could be extending the time to get the engine to an efficient operating temperature and/or keeping the air colder (more dense) than the stock system.

There are a myriad of normal contributors that are part of a cold weather reduction in mileage, many previously mentioned, that there is nothing you can do except wait for warmer weather.

[racingbmwm3]

2 things you can do to increase your gas mileage.
1. park in a heated garage - all fluids will start off at a 'warm' state, so less time to heat up
2. install a block heater - the engine will be 'warm' and won't take as long to heat up, other drivetrain parts still cold though.

[ExpensiveTaste]

One reason I haven't heard yet is rolling resistance. With all the snow we've been getting, that's increased resistance on the X rolling forward, increasing the force needed to push the vehicle...Does the X increase shift points to warm up the engine faster?

[racingbmwm3]

rolling resistance would be hard to determine...deep snow, ice, wet roads, dry cold roads...Yes, rolling resistance in snow and rain is higher making your mileage worse. To go with that are the slower speeds you should be travelling at which again are another hit on the mileage.
Also if your traction control is coming on all the time (because you have all seasons and not winter tires) your both wasting gas and brake pads.

No, opposite would occur in slippery conditions, the transmission will shift sooner keeping the RPM's down to prevent excessive wheelspin. Transmission doesn't care what the engine temperature is regarding shift points.
If in (deep) snow, you should have DSC off, *and ideally transmission in Sport or Manual mode

*disclaimer, watch out for hidden obstacles under the snow...