Here's my $0.02, at least regarding newer 1.5L FIT, ex. 2018:
I'm a firm believer that our FIT's oil should be changed every 5000 miles.
I did let my oil go to 8000 miles, with the oil life indicator still good, and didn't like the color of the oil coming out. Yes, I'm sure that it's still "good", but why push it??
Oil is cheap, especially if you shop around, ex. Walmart.
Filters are cheap: I purchased a 10-pack of OEM filters off of Ebay at a great price.
Taking the bottom cover off is fairly easy and straightforward.
Overall, the job is quite easy.
Our crankcases don't even hold 5 quarts, but more like only 4 quarts with a new filter. I drive my FIT hard, and never want an oil caused issue.
BTW, I picked up a "case" of Valvoline 0W16 at a great price($27/5 quart) at NAPA on a special promotion. This is oil that should give us a bit more fuel economy. Testing was done on a FIT, and I believe we should expect almost a 2% increase in fuel economy. Over the summer I was approaching 37mpg, like 36.5mpg, so a 2% increase may push me over 37mpg. Unfortunately, it's winter now, and my fuel economy has gone down quite a bit, as I'm only getting about 35.5mpg now, due to NJ's winter-blend gasoline.
BTW, A Honda Goldwing oil filter/plug wrench works on the FIT. :-)
Oh, a quick comment to the person who is using "Dino" oil:
- Come on man, go to Walmart, a 5 gallon jug of 0W20(full synthetic) is presently only $15.98!!! Gone are the days of $5+/quart for full synthetic, now with the option to purchase 5 quart jugs. Walmart isn't the only game in town either: Amazon Basics 5 quarts 5W30 $17, 0W20 $20, again only a $3 difference!!! Amazon Prime too.
- You are losing fuel economy.
- Our Honda FITS have very tight tolerances, and really prefer oil that is quite thin. Anything thicker than 20W is going to cause unecessary added fluid friction.
- Going from 0W20 -> 0W16 was tested and provides ~2% better fuel economy with using an oil that is only marginally(20W -> 16W) thinner (google search "Honda Fit 0W16 Oil)
- Going from 0W20 -> 5W30(assuming that 20W dino oil isn't common), or 20W -> 30W, a 4% lost in fuel economy would not be out of the question.
- Walmart 5W30(Dino), $12.88, is only $3 less than 0W20(Full Synthetic). Over 5000 miles(oil change interval) with 4% loss in mpg-> ~200 miles ~ 6 gallons of extra required fuel -> $13.50($2.25/gal) VS spending $3 more for full synthetic!!! And don't forget that cost difference is even more, because we're only using 4 quarts out of each jug for our oil changes. Even if loss was only 2%, it's still cheaper in the long run to use full synthetic.
- In summary: Its cheaper to use 0W20(Full Synthetic) VS 5W30(Dino), as the savings at the pump will more than pay for cost premium of purchasing full synthetic VS Dino oil. Plus you won't be violating your car's warranty. I didn't check, but Honda most likely mandates that synthetic oil is used in our cars as hinted by the fact that our filler cap has "0W20" printed on it. NOTE: 0W16 is typically much more expensive compared to 0W20, more so than the cost one would save with the added fuel economy. I just happened to catch a great sale and wanted to see if I could observe and actually see my FIT's summer EPA surpass 37MPG(mainly city driving). But, as soon as 0W16 becomes mainstream and almost as inexpensive as 0W20, this would be the preferred oil for us to use in newer FITs, and also in many other newer vehicles, ex. Toyota is starting to mandate 0W16 to be used in their newest models.