Hey everyone! I have a 2017 Miata with a standard transmission and was wondering if the issue I am having is normal. At 70 mph my Miata gets about 42 mpg, but when I go 80 my Miata gets about 20 mpg. The car doesn't shake or run rough and I am cruising on a leveled surface while also trying cruise control. As always thank y'all for the answers.
At 70 mph my Miata gets about 42 mpg, but when I go 80 my Miata gets about 20 mpg.
The faster you go the more air resistance you encounter and the more fuel you'll use.
At 70 mph my Miata gets about 42 mpg, but when I go 80 my Miata gets about 20 mpg
This is the precise reason why the "Worldwide Harmonized Light Vehicle Test Procedure" (WLTP) shows a few assessments for efficiency.
For a Miata MX-5 (1.5L, 6 speed manual) it's:
- Fuel Consumption (WLTP Extra High): 6.6 l/100km (36 mpg) - up to ~80 mph
- Fuel Consumption (WLTP High): 5.4 l/100km (44 mpg) - up to ~60 mph
- Fuel Consumption (WLTP Medium): 5.9 l/100km (40 mpg) - up to ~47 mph
- Fuel Consumption (WLTP Low): 7.9 l/100km (30 mpg) - up to ~35 mph
-
Fuel Consumption (WLTP Combined): 6.3 l/100km (37 mpg) - what to expect realistically.
As you can see, above 60, the faster you go - the less efficient it is.
You can search for the exact WLTP rating of you exact car online to know how efficient it should be at what speed.
Not gonna lie I've never even heard of them til right now. However, according to that I should be getting closer to 36 mpg rather than 20 mpg, so do I do the normal troubleshooting of bad gas mileage (air filter, clean maf sensor, clean fuel injectors, etc).
The specs, as I stated were for a 1.5L, if you have the 2.0 and have the factory 180 horsepower tune on it - it's significantly less efficient.
You can do the basics troubleshooting steps at your risk but considering that at low speeds it performs just fine it seems alright to me.
was wondering if the issue I am having is normal
Here’s your introduction to aerodynamics -
Same gear, same road? Is that current consumption when you accelerate from 70 to 80 or is that difference in average gas mileage?
Same gear. Same road. It is average gas mileage.
What gear at what RPM?
At 70 mph about 2900 at 80 mph about 3100.
EDIT: This is solely based on memory I don't know the actual rpms, but I'm definitely sure its in that ballpark.
Is that difference new or is it present since you have the car?
Honestly, I have only recently been concerned about my gas mileage. Up until a month ago never even looked at average mpg at specific speeds only average mpg for town and highway driving which I have noticed it going up but at a lower rate (when I first got the car it had about 50000mi and 28 mpg and now has about 75000mi with about 34.6 mpg).
So you only look at what computer shows you or you also verify if it shows real consumption when you fill the tank?
Only what the computer is showing me.
It's good to check out if it shows real consumption.