Author Topic: Question for the smart guys... (Read 3382 times)

troman · « **on:** February 21, 2012, 12:03:39 PM »

I have an e30 m42 318i.

I swapped in H4/H1 Hella headlights.

I swear that when I have the lights on, I'm getting less gas mileage. Like, the difference between 22mpg and 25mpg in mixed and spirited driving.

Is that possible/probable? Why?

TIA...

DesktopDave · « **Reply #1 on:** February 21, 2012, 05:11:26 PM »

Well, I'm not a smart guy, but I'll say no, it's not possible. Unless you're pulling some serious wattage. Stock bulbs are what, 50 watt? If you were using 100w maybe it'd be like that...

deansweet · « **Reply #2 on:** February 21, 2012, 05:58:04 PM »

Have you had the car long enough to know what the car mpg averages normally during the cooler part of the year? Only thing I can think of is that maybe the new lights corresponds with the onset of winter when the gas gets additives and your car uses more fuel to function(this is all normal)?

Does that make any sense?

troman · « **Reply #3 on:** February 21, 2012, 07:38:24 PM »

deansweet - Yes, totally possible. This is my first winter with the car, so I don't have a baseline. I was averaging 25mpg this summer, but seem to be around 22 lately.

But at the same time, I feel like I can detect some changes in the car when I flip the lights on. Idle a little higher, maybe. I have a brand new Interstate battery, and the H1/H4s are just regular wattage.

Does anyone ever relay their H1/H4s? I'll search for that.

Thanks for the replies!

DesktopDave · « **Reply #4 on:** February 21, 2012, 08:26:17 PM »

With the >10% or so gasohol we have here, spring & winter fuel cost me 2mpg over the last 2 1/2 years.

Could be a double whammy too. I noted that good brands of 93 octane fuel (5% or less alcohol) did best, 31.1mpg. It beat 91 octane (26.7 mpg) by almost 5mpg! Even 89 octane (29.3mpg) beat out 91, unexpectedly. That grocery store-discounted fuel is pretty bad too, but I won't look a gift horse in the mouth.

BTW, the headlights are already on relays. K4 is low beam, K3 is high beam and K8 is fogs. Check the low beam relay...might be cooked. I've seen that with the main, fuel pump and especially the unloader relays.

keflaman · « **Reply #5 on:** February 21, 2012, 10:45:04 PM »

I'd suspect the winter blend of gas as well. My Jeep loses ~2mpg in the winter...I need to finish my car and get it on the road fast!!

troman · « **Reply #6 on:** February 23, 2012, 01:22:37 PM »

Thanks for the suggestions, guys!

BETTERTECH824 · « **Reply #7 on:** April 26, 2013, 02:46:45 AM »

Hold up, wait a min, the head lights effecting gas mileage?
Am I missing something?

I'm an idiot and I know there isn't anyway your headlights are effecting your gas mileage!
Isnt that like saying my radiator keeps popping fuses?!?!?
the 2 have nothing to do with each other...
maybe Im wrong but if so please correct me.