When we bought it was averaging 32mpg with 18x7's on it. Recently the gas mileage has dropped to 26mpg or so. The only changes since the drop in gas mileage was we switched over to Castrol Fully Synthetic 5w30. Best I could tell it had a conventional in it when we bought the car. Only thing I can figure is that the oil has already begun breaking down. I had read some where else on the board that the xb likes Pennzoil platinum should I possibly just try the switch to that and see if fuel economy returns? There is approx. 2500 miles on this oil change anyway.

Any suggested welcomed and thanks in advance!

 

Never use penzoil-even though they are not supposed to be putting parafin in there they still do.

Check where you get gas-I had the same problem right after labor day-dropped from 30-31 average including around town to like 26-27. They started using 10% ethanol in all the gas instead of just winter gas and it killed mileage for me.

Once you use synthetic you also cannot go back to regular oil supposedly-causes problems. Check you air filter as well-that could be hurting things-maybe spark plugs too.

 

Yeah honestly Mobil 1 or AMSOIL are my favorites. My evo has been on Mobil 1 since day one and everything internally was still in excellent condition when i installed cams at 70k miles. Ill probally go back to Mobil 1 when i change it again as i never much cared for Castrol.

Plugs are the next thing on the list to replace. We are getting gas from the same station but some how that station has started staying around 10cents a gallon less than other local stations. I also already replaced the air filter when we first bought it and got a decent jump from that.

Im basically just going to assume that most all of the stations locally have gone to 10% ethonal as your said because of winter. Once the weather got cold is when we noticed the dip in gas mileage.

 

A few misconceptions need to be cleared up:

1. All major motor oils, in fact, are formulated using a paraffin-based crude oil. Naphthenic-based crude oils are actually more likely to form sludge in an engine than oils formulated with paraffin-based crude oils. This is due to the higher breakdown resistance of paraffin-based crude oils. Take a look at the MSDS for Mobil oils - or almost ANY oil for that matter - they all contain paraffin. Additionally, if you look at UOAs you will see that Pennzoil dino is one of the best performing motor oils there is.

Synthetic base stocks are 100% paraffinic. Technically, paraffinic oil is a term used to describe the chemical structure, not the wax content. Through dewaxing in the refinery and the addition of pour point depressants during blending any harmful effects of wax are eliminated or neutralized.

A paraffin is just a common name for a saturated C-H chain (hydrocarbon chain). In chemistry they are known as an alkane. The term paraffinic base oil is derived from the term paraffin, meaning a saturated hydrocarbon based oil.

Almost all motor oils contain, or, are mostly paraffin's (alkanes), including Group I, II, III, IV and many oils in Group V. The exception in motor oils are the ones based on esters (Group V) and other oils which are not paraffins in Group V, but a motor oil using only ester base oils is rare.

Paraffin is sometimes confused with paraffin wax. A paraffin isn’t necessarily a wax. There are paraffin type compounds and then there are paraffin waxes. The shorter paraffins (alkanes) like methane (CH4) and ethane (C2H6) are gaseous at room temperature. As the hydrocarbon chain gets longer ~ 10C, the C-H chained molecules become liquid at room temperature (oils), and when you have a long straight chain with ~20C atoms or more, the molecules will form a crystalline structure at room temperature known as a wax.

PAO's are made from alkenes, which are not paraffins (alkane's). Alkenes = olefin = C-H molecule with at least one double C=C bond. Modern PAO's are hydrogenated to remove any remaining C=C double bonds (saturate the carbon atoms with hydrogen) to increase their thermal/oxidative stability, which in effect turns the chained alkenes in the PAO into alkanes, which are paraffin's. So, hydrogenated PAO's (Group IV) are paraffin's too.

Here is a link and sample of a journal that refers to this.
http://www3.interscience.wiley.com/j...68648/abstract

"Abstract
This study was conducted to determine the effect of hydrocracked base stock chemical composition on lubricant properties, oxidation performance, and antioxidant additive response. Fifteen hydrocracked base stocks and polyalphaolefins were analysed by mass spectrometry for paraffinics, and single-, double-, and multi-ring naphthenics. Low levels of aromatics were confirmed in all the base oils. A linear relationship was found between certain naphthenic structures in the base stocks and properties, such as viscosity index, aniline point, and volatility. Additivated versions of the base stocks were also screened in the rotary bomb oxidation test (ASTM D 2272) and the thin-film oxygen uptake test (ASTM D 4742). A relationship between the types of naphthenic structures in the additivated base stocks and oxidative stability was found. Base oils containing low levels of condensed multi-ring naphthenic structures exhibited superior oxidation performance, lower volatility, and poorer solvency. Furthermore, antioxidant structure had a profound effect on oxidative stability as the level of multi-ring naphthenic structures in the base oils decreased. These results suggest that deeper knowledge of chemical composition could help in selecting base stocks and additives to meet future product specifications."

2. Have you never heard of semi-synthetic oils? You can switch from dino to syn and back again as often as you want - it wont hurt a thing.

 

The only way to know FOR SURE what is a good motor oil or not is with used oil analysis (UOA). If you look up UOA for OUR MOTORS that run M1, you will see just how weak it really is IN OUR MOTORS. Some motors might really like it (actually, many motrs do like it) but in OUR MOTORS, it is a poor performer. Many dinos show better wear numbers than M1 IN OUR MOTORS.

 

I have heard the misconception about not being able to switch back and forth i always kinda just ignored this as i knew it was incorrect.

 

What is the best oil for these motor's its not actually my car I drive a 97 Honda and an evo. Its my wife's car I just change the oil and do the maintenance to keep her rollin;)

 

are you sure you are not driving differently? maybe you are pushing the gas a little harder to pass more people or from a stop light? whenever i notice a drop its usually because i know was hitting the gas a little more than usual

 

The driving habits are exactly the same. I xb's arent fast so there isnt much point in driving them hard. None the less we are going to attempt the first suggestion and look at what fuel we are using and go from there.

 

According to UOAs, PP 0w20 or 5w30 is best for these motors.

 

due to the time of the year with the colder weather and winter blend gas

i get better mpg in the summer then i take a 5-6 mpg hit in the winter its normal

 

is it really a winter blend of gas? Honestly that sounds like total crap to me. If you think about it, in the winter people usually let their car idle to warm up therefore wasting gas. Secondly the cooler temps are read by the air intake temp sensor and it adjusts the fuel injection accordingly. Cooler air = denser air which equals more fuel needed for an efficient burn.

gas is gas... it takes a lot to freeze so why is there a change in formula?

 

there really is a winter blend gas... so heres a bunch of links to read about winter blend gas

http://www.msnbc.msn.com/id/14806032/

http://www.theoildrum.com/story/2006/9/13/234043/431

http://www.csnews.com/csn/news/artic..._id=1003121829

http://www.eastvalleytribune.com/story/99391

http://www.slate.com/id/2098672/

 

well good to know. I never really cared that there was a different blend or wondered why. But not that I read about the EPA having restictions on the volitile pollutants that easily evaporate in summer temps it makes sense to me now.

But with a MPG drop in the winter but cheaper prices sucks, makes you think you are getting a nice deal almost. Unless you are up-to-date on the oildrum.com website.

Man... Just blows my whole thoughts for the day. Oh well a lesson learned.

Thanks for the links!

 

I notice a large drop in mileage for my '04 xB too. I just recently put on new rubber, had the plugs changed, oil changed, even replaced the PCV valve, and I've always used either Mobil 1 10w30 or Valvoline 10w30, fully synth.

I would average at least 75 miles for each of the 4 gas level readings, and the low fuel light wouldn't come on until about 290-300 miles. Now I get about 50-55 per quarter, and the low fuel light comes on at about 240.

I also thought about maybe putting a tank of higher octane fuel, to clean the injectors. Just curious, anyone used av-gas in theirs without any problems?

 

have you tried to use 5w30 in your xB???

 

No, not yet. I've been using 10w30 for awhile, and have only noticed the drop in the last month. At the moment I'm going off the assumption it's because of the "winter blend" of fuel.

 

I too use Mobile 1, also check air filters, tire air pressure.

 

I haven't changed the air filter yet (and I know I need to). Is it worth getting something aftermarket? I don't plan on a complete CAI system or any major mods, but I know that generally the stock air intake systems aren't the the most efficient, or don't let the engine breather as well as it could, so I'm open to opinions. What have you all found work as a good after market replacement?

 

I would honestly stick with the stock filter. Like I said, I used short air intakes or aftermarket drop ins on all of my vehicles and lost fuel efficiency in every one. Sure an intake sounds good but I would rather better economy over sound.