Ever Notice You Get Less MPG Just After an Oil Change?

Folks here clearly not used to looking at a full-blown performance vehicle (Ferrari) with a 60 grade. These kind of oils typically shear down somewhat quickly from the UOAs I've seen posted. NOT a '99 Camry driven to the store with ST 5W30 🤣
 
I've never seen MPG change in old oil vs new oil in any of my vehicles. However I do see a drop in MPG in cold weather in all my vehicles. Could this be what you are seeing?
 
Never ever seen a fuel mileage drop when changing the oil in anything. Not just cars or pickups, but also not in an atv, semi truck, or anything else. Now if we are discussing summer vs winter mpg, then its a substantial drop in winter. So if you change your oil the same day that your local gas station switched to winter blend fuel, then you are going to see a sudden decrease in mpg.
 
I've never seen MPG change in old oil vs new oil in any of my vehicles. However I do see a drop in MPG in cold weather in all my vehicles. Could this be what you are seeing?
He lives in Sarasota Florida, which is experiencing some cooler weather at the moment but overall it’s not had sustained cold temperatures enough to make any difference in fuel consumption
 
Right now we have 40-50 degree nights and 60-70 degree days. And yes, the MPG overall is less than mid-summer. Regardless there has been, over the years, this trend in my "regular" cars and trucks just after an oil change. In these cases the slight drop in viscosity grade (if at all) would probably play a small role. I think there is something else going on. My routes are very repetitive. Just after this recent oil change in my GMC Yukon I am suddenly getting a solid 1 MPG less. I was getting 19-20 and now getting 18-19 MPG. And I am one of those guys who follow this sort of thing. I love the trip gauge that resets with each start of the engine. I have a second gauge I reset when I fuel up and a third one that I reset after an oil change. I know, anal but it's me.

Ali
 
I love the trip gauge that resets with each start of the engine.
You should calculate your fuel mileage by hand, and do it after a full tank of consumption. In every car I've checked, the trip computer calculations don't match reality - and by a greater amount than the fuel mileage differences you claim.

And make sure you fuel and refuel at the same exact pump location at the same station. Fueling on the same spot eliminates any variables with how much the tank fills because of differences in the surface grade or slope.

And even if you do all this, how are you going to replicate the exact same route over a full tank of fuel? Winds, temps, getting caught at red lights or not, variations in how you drive the same route depending on whether or not you're in a hurry, etc.

Your methods tell to me your Yukon gets 18-20 mpg and old or fresh oil has nothing to do with it.

Scott
 
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Right now we have 40-50 degree nights and 60-70 degree days. And yes, the MPG overall is less than mid-summer. Regardless there has been, over the years, this trend in my "regular" cars and trucks just after an oil change. In these cases the slight drop in viscosity grade (if at all) would probably play a small role. I think there is something else going on. My routes are very repetitive. Just after this recent oil change in my GMC Yukon I am suddenly getting a solid 1 MPG less. I was getting 19-20 and now getting 18-19 MPG. And I am one of those guys who follow this sort of thing. I love the trip gauge that resets with each start of the engine. I have a second gauge I reset when I fuel up and a third one that I reset after an oil change. I know, anal but it's me.

Ali
Shouldn’t you be getting better MPG with the type of weather you are having now since it’s really not anywhere near what most people would consider cold and you also don’t need to use the AC like you would in the summer?
 
I too have noticed lower MPG after an oil change however, it is not exclusively every OCI.
What I have also noticed is that my MPG is never higher/highest after an OCI.
ATMOF, my best MPG is best before my next OCI.
I use our summertime as my guideline as this is when my MPG is most consistent.
 
Shouldn’t you be getting better MPG with the type of weather you are having now since it’s really not anywhere near what most people would consider cold and you also don’t need to use the AC like you would in the summer?
I think all A/C units today are variable vane and always on. Here the humidity is always so high the vehicle would fog up inside if the A/C was totally off.
 
Anecdotal evidence I see an increase in MPG after an oil change. I have my trip b set for miles on my tranny fluid and trip a set for oil. Trip B has almost 8k miles, where the trip A gets reset around 4-5k. After a change trip a is much higher mpg than trip b.
 
You simply can’t control enough variables to make this a valid observation given the differences we’re talking about here.
 
Exactly. It's called "winter blend." That there petrol simply has less energy vs the rest of the yr.
Yes and add to this the reservation sells 87 octane non ethanol gas. I constantly get 2 - 3 MPG (depending on the vehicle) better gas mileage over the10% ethanol gas.
 
I think all A/C units today are variable vane and always on. Here the humidity is always so high the vehicle would fog up inside if the A/C was totally off.
The AC in my 2018 Corvette and my Civic only comes on when I activate it. I know this because you can see a pretty noticeable MPG drop in both cars with AC on, so I don’t use it often
 
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