Fuel economy...

"RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars" (rallydarkstrike) 11/25/2018 at 07:07 • Filed to: Oppohelp

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Hi Oppo!

So, I know it’s winter and I now have my winter tires on, so my fuel economy (of course) drops this time of year...however, I notice it’s been noticeably lower the last few months than it always used to be.

In the Spring/Summer I could often get 620km or so to a tank, and then around 580-600km in the colder Fall/Winter months. Lately though, I’m getting more like 530-550km in colder temps and 580km in warmer temps...that’s quite a drop!

I had slow leaks on 2 of my All Season tires that I had to constantly fill up during the warmer months, so that wouldn’t have helped, but I kept them topped up mostly, so I can’t think it would’ve affected the fuel economy that much...? I’ve checked the air filter and it’s not 100% clean, but it’s certainly not clogged at all, just a bit dingy. I also took out and cleaned my car’s MAP sensor in case it was dirty and not reading correctly...that made no difference either. One of my wheel bearings went in the summer so that could’ve also contributed, but it’s replaced now, so no more drag from that...

Can anybody think of another reason I am overlooking other than brakes dragging or some such? I don’t seem to feel the brakes dragging or the like and when I had my winters swapped on / my last oil change done, the mechanic didn’t notice any extra drag on the wheels from sticking brakes or anything...?

It’s a bit puzzling! Cheers! :)

rillweid - Now with more TRD and less TDI > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 11/25/2018 at 07:18

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Fuel blends are different in the winter which could be contributing. 

pip bip - choose Corrour > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 11/25/2018 at 07:28

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put more air in the tyres?

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > rillweid - Now with more TRD and less TDI 11/25/2018 at 07:30

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True, yes, but why was my economy dropping from what it normally was in the Spring/Summer as well?

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > pip bip - choose Corrour 11/25/2018 at 07:31

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I’ve always kept them at the recommended 32psi and that’s where the figures came from above, so I should need to put a tad more than the recommended in there!

E90M3 > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 11/25/2018 at 07:52

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Pretty sure it’s due to the actual content. Winter blends contain more hydrocarbons with shorter chains. Pretty sure that the shorter chains contain less energy than longer chains. The reason the blend is chained is be cause of temperature and vapor pressures and things like that. 

MultiplaOrgasms > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 11/25/2018 at 08:12

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Recommended pressures are only for comfort and handling purposes. You can easily run 45psi for better mileage without greatly compromising the former. The tires can usually handle quite a bit  more than what the inscriptions say. 

duurtlang > MultiplaOrgasms 11/25/2018 at 08:35

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Would you not get uneven wear that way? With the middle wearing out while the sides still have loads of thread?

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > duurtlang 11/25/2018 at 08:41

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That’s why I keep mine at recommended....I’ve had some wear wrong from low pressure before (slow leak that I didn’t know about until it was too late) and pumping them up more would tend to wear the center of tread out more quickly than the sides, would it not?

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > E90M3 11/25/2018 at 08:42

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But my point was that with the same blends, I got more economy in previous years than I am this year, so something has had to change I would think...?

E90M3 > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 11/25/2018 at 08:51

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I had to re-read your post. It looks like something is wrong with the car then. I know my 3 had a CEL on at some point and the code was pointing to a timing sensor, cam or crank or something. So I’m pretty sure the car was retarding timing and dumping extra fuel into the cylinders. 

MultiplaOrgasms > duurtlang 11/25/2018 at 09:17

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At only 3 bar of tire pressure, not so much. Both me and my dad run 3 Bar on our tires and at that pressure the Tires don’t really balloon at all. The tires last just as long as with lower pressures (Speaking from my dads perspective, 4 0.000+ km per year etc , using standard issue Michelin Primacy and Pilot Alpin )

Sovande > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 11/25/2018 at 09:22

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Spark plugs, air filter, fuel filter, fuel pump? Or it could be something like a hanging parking brake?

I own dead car brands only > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 11/25/2018 at 10:09

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There is also the possibility that the fuel blend isn’t exactly the same as the previous year. I remember noticing my dearly departed Saab getting much worse fuel economy compared to previous years. Realized that because it was much colder and the engine had to dump more fuel to keep it running. The smaller the engine the more fuel needed to keep it running and up to temperature.

As always, YMMV

GoodIdeaAtTheTime > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 11/25/2018 at 10:13

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Pull your oxygen sensors (yup all of them) and take a look at it. Look for any discoloration of heavy sooting, replace as needed . If you know a good technician, see if they  can do a back pressure test on exhaust components. Could have a wonky sensor, or a catalytic converter or muffler clogging up affecting mileage. Maybe check for intake leaks, if it is running a bit lean the ecm will compensate with extra fuel.

Personal note: Overall fuel quality has been dropping. Something I have noticed in the last few years... I’ve sent many samples to labs in the last 5 years or so and more and more crap is finding it’s way in. It is an easy and sneaky way of trying to dispose of industrial waste (I THINK, totally debatable. If I can round some of the sample results I’ll try to post them). I work close to an engineering level as a diagnostic tech for a large Asian car brand. Lots of complaints of lessening fuel mileage. Fun stuff to figure out. Their engineers are very interested in what I’ve been doing. Maybe a promotion is in order?

If you use regular stations, find a different one a little further out. More rural stations tend to have a better fuel quality overall. Who knew?

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > I own dead car brands only 11/25/2018 at 10:35

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Could be that the quality is less than it had been in previous years then perhaps!

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > Sovande 11/25/2018 at 10:36

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If the parking brake is sticking, it can’t be by much....it seems fine though as I use it all the time!

Checked the air filter, dingy, but definitely not clogged. Could be fuel pump, but I’ve had them go in previous cars and usually noticed an audible whine before they kicked the bucket...this one seems to sound fine still at least, and the car seems to run as it always did, just get worse economy. Spark plugs were just changed in the summer , so they SHOULD be OK?

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > E90M3 11/25/2018 at 11:29

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No CEL, but yeah, it seems off somehow...

Spamfeller Loves Nazi Clicks > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 11/25/2018 at 11:35

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Run higher PSI in colder temperatures. Cold air is denser than warm air. Means that the volume in the tire is lesser at the same pressure in colder weather. Take the door, add 3 PSI to start. May be necessary to go higher than that, depends on the car, load, roads, temperatures, and tires themselves.  

Akio Ohtori - RIP Oppo > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 11/25/2018 at 12:16

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Car warming up ok? Temperature readings seem reasonable?  A bad thermostat or bad coolant temp sensor would cause a drop in MPG.

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > Akio Ohtori - RIP Oppo 11/25/2018 at 12:27

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Seems to warm up fine! Base trim Accent means no temp gauge, just an idiot light, but I get heat from the HVAC vents a little bit faster than mom’s car, so it seems to warm up quickly and then stay at temp no problem (according to the recent drives I’ve done with my Torque Pro app and WiFi OBDII connector running, anyway...I have my phone display set to show coolant temp ).

Longtime Lurker > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 11/25/2018 at 13:31

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What brand of spark plugs came out what brand went in?

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > GoodIdeaAtTheTime 11/25/2018 at 15:10

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Very cool, sounds like your job is interesting!

....I don’t have the space or tools (like a jack other than the tiny one that comes with the car) for checking the O2 sensors underneath, sadly , so if it doesn’t get better I might take it somewhere to get looked at...

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > Spamfeller Loves Nazi Clicks 11/25/2018 at 15:11

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Ah yes, never even bothered to think of that, might pump them up a bit extra tonight then!

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > Longtime Lurker 11/25/2018 at 18:04

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Not sure to be honest! I had them replaced when the car went into the dealership to get recall work done on the brake light switch. It was misfiring at the time (which turned out to be a coil) but the plugs were due, so they did them at the same time.

Longtime Lurker > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 11/25/2018 at 18:08

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Well the dealership would have installed good plugs. sometimes aftermarket plugs can cause differences in fuel economy.

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > Longtime Lurker 11/25/2018 at 18:10

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Yeah, true. This has happened since the plugs were changed though, not right after it.

Future Heap Owner > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 11/26/2018 at 13:21

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So you’re back on the winter tires now, and you’re still getting worse economy than last winter?

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > Future Heap Owner 11/26/2018 at 14:44

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Exactly, I was also getting worse economy than usual on my summer tires as well. I know they had a slow leak (2 of them) , so economy should’ve been expectedly a bit lower, but it was like 30-40 km lower than usual...?

Future Heap Owner > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 11/26/2018 at 15:22

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I’ve seen my economy decrease by 5-10% from running a few PSIs low in my tires, so that sounds plausible to me. But the fact that it’s happening on both points to another cause (dunno what it would be).