Question about tire repair

I still have the spare from my 93 NA, with a faux leather donut jacket. The spare in the 79 SA is a proper full-size, I remember that was the first time I ordered a set of five tires.
 
Well you aren't supposed to use the spare on a drive wheel, despite many not knowing that. Also, it won't even fit on the turbo front brakes, so you must use it on the rear. There is no other way.
I was more concerned with how the smaller diameter spare on the front might affect the inner workings of the front transaxle, rather than vehicle handling. But if the dang spare won’t even fit on the front, the point is moot. Mazda dances around that tidbit of information in the owners manual. Thanks for the info.
If I remember correctly… when airing up my spare today, I noticed the spare uses a 17" wheel. The other four are 19"
 
After 500+ miles, the mpg is now around 35. I checked the tire pressure today and all 4 were around 34. I suppose the shop's tire inflator (running from an air compressor) would read differently from my cordless handheld unit. However, the door jamb sticker says 36/33. I thought it makes sense for the CX-3, not because she's got a Skyactiv 3.0 in the front, but that her rear end is short and light.

What's the reason for having all four the same? I have heard before that 35 all around is a safe bet on most cars.

I replaced the intake air filter too.
 
Tire pressure is based on load. My Miata only calls for 29 psi due to the lesser weight on the tires.
 
Tire pressure is based on load. My Miata only calls for 29 psi due to the lesser weight on the tires.

Same for my SA. This sticker says 26 psi. But the lube place did 35 anyway.

Just noticed that the weight capacity is 340 lbs. The only time I went over that was when riding with a 230+ lbs dude. 🤦
 

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