Oil weight observation and fuel economy

I ran 0w20 PUP in my odyssey for the first 3/36. After that it’s been PPE 5w40 and also muzzled the VCM. Fuel economy pretty much the same to my untrained gauge calculation.

I can up my mpg just not using the ac and hitting a few less red lights on a drive lol
I've just driven from San Francisco to Chicago. The oil has remained the same the entire trip (maybe it thickened some, maybe it thinned).
My gas mileage varied a bit with each tank from a low of 33.something to 37.21. I tried very hard to keep the engine within a certain RPM range the entire trip. The only thing that changed was the gasoline ... and the wind direction, the number of times I stopped to pee, how many trucks I was stuck behind, the ambient air temperature, the humidity, the number and degrees of the hills I climbed or went down ... and here's the weird thing: I believed at various times on the trip that I could tell if I was getting better or worse mileage based on how the car felt. That turned out not to be so. In one instance, when the car felt the worst, the mileage was among the best I achieved.

Bottom line: Butt dynos mean squat.
PS: All mileage figures were manually calculated.
,,,also whether the car was leveled precisely the same at each fill-up, if the fill-up was identical in completeness, if the various pumps were calibrated to provide exactly the same volume reportedly pumped, if the temperature of the fuel at each station was exactly the same, if the composition of the fuel at each station was exactly the same, if your tire temperature was always the same, if the road surfaces had the same friction, and if you had a big ole dragonfly smashed to your bumper that fell off at some point....among other variables not listed....
I'm currently running Red Line 20W-50 in my car and experiencing some of the lowest fuel consumption rates in it's life. Go figure, twice the OE HTHS....
"Oil weight observation"

This oil matches this price. :ROFLMAO:
I want to add something. In reality there is no doubt that MPGs suffer when increasing HTHS. We must remember that the differences are measured in a controlled operating environment. Due to the comparatively uncontrolled environment of day-to-day usage it's unlikely that the customer can replicate the difference nor should the customer expect to. This is something we should always try to remember before we give into the urge of our own confirmation biases.
FWIW we just took a 1700 mile trip to Canada and back. I used 87 E10 for the trip (** we left the house on 88 E15) and my mileage is listed below. All values are from my Fuelly app so hand calculated. We traveled a total of 1703 miles, spent $302.76 and used 69.558 gallons, averaging 24.5MPG. IMO, driving conditions (highway/in town), speed, and weather (temperature and humidity) play a much bigger factor than the oil viscosity.

26.3mpg, 29.0mpg (average 27.1mpg) - to Canada at various speeds but usually between 75 & 80MPH, temps cool at 70 - 75F, low humidity and no wind
22.3mpg, 28.1mpg (average 23.8mpg) - in Canada for various in town and short distance trips
23.8mpg, 20.9mpg, 24.5mpg (average 23.3mpg) - home to Iowa, again various speeds but between 75 & 80MPH, temps hotter at 85 - 90F and humid, mild wind w/ some gusts

just my $0.02
This will be a factor of a couple of things : the HTHS viscosity is one of those.

I am going to assume this is an A3/B4 or C3 application. So minimum HTHS is 3.5.

The 5W-30, if it meets spec, is likely to be 3.5-3.6 HTHS. Being I’ve seen quite a few Pennzoil Samples lately that were thinner than spec…. I have some reasonable doubts.

The Valvoline is 3.9-4.0 HTHS. It’s effective operating viscosity is 12.5% higher. Supposedly, this can account for quite a bit of drag in the engine.

Also, there is a huge range in acceptable pumpability and cold crank simulation scores for a 5W rating. If the 5W-30 formulation actually has a significantly reduced MRV viscosity, it’s entirely possible that during the warmup phase the mpg difference could be excessively high!

Then, there’s potential differences in the additive packages - perhaps one has a bit more Moly, or other additives that will further reduce frictional losses.

At the end of the day, the difference you are seeing on the dash is likely due to the engine seeing a reduced MAP/MAF signal and lower loads, resulting in less fuel consumption, and a higher displayed number based on its calculations. Or the opposite if you’re talking about the 5W-40. How closely that resembles the real world - whole other story…

There’s also the fact that other 5W-40s may not exhibit similar losses due to the formulation, additive package, and such.