Will one oil give you better mpg? Make your engine last longer? 

Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
Do a search there are countless threads on this. Also, go check the oil FAQ on the 80 board.
One way to start a discussion with widely-varying opinions - ask about the best oil.
Pretty much everyone agrees that a good 100% synthetic is superior to conventional. Beyond that, get ready for disagreements.
My own .02: Synthetic, change oil & filter at shorter conservative intervals ("severe" service interval, or 5k miles in the 1999 100 Series). This is the K.I.S.S. method absolutely guaranteed to assure extra-long engine life & best fuel economy.
(Actually, for a run-of-the-mill vehicle, I don't believe synthetic is worth the cost, as long as the change intervals are shorter "severe service" intervals. But the LX470 deserves synthetic.)
Counterarguments:
1. Test your oil, with the goal of determining when it needs changing, rather than simply change at regular shorter intervals.
(How much does it cost to test - including your time & S&H etc.? My time carries a steep premium. What is the possibility and extent of test error? What criteria should you apply in deciding when to change? Where did that criteria come from? Are you absolutely certain it correlates to actual engine wear factors? What if you are wrong or test is erroneous? Is the risk and cost worth it?)
2. One brand/type of synthetic (or other) is better than another.
(Good luck proving this. I am not aware of reliable unbiased conclusive data proving one is better than another, and no, UOAs alone or mfg claims don't prove it to me personally. I pick Mobil 1 because Mobil, being a large corporation, has both the resources to develop and produce a quality oil in quantity and also the resources to lose big-time if they screw up, so I figure they are probably about as good or better than any other synthetic - and, Mobile 1 is widely available and moderate cost, unlike the boutique synthetics.)
One thing folks may forget, when advocating extended change intervals using boutique synthetics, is that the oil is actually a cleaning agent in the engine, in use. The filter catches some but not all of the particulate, and the various additives mitigate partly but not fully the various chemical contaminants, that accumulate in the oil over the service interval. I don't want to leave it in for longer service intervals partly because I want to get that used cleaning solution (oil) OUT, replaced with fresh cleaning solution (oil), on a very regular basis. So far (>25 years and a number of vehicles), this has produced excellent results, with least risk.
Now, bring on the soapboxes! hehe
One way to start a discussion with widely-varying opinions - ask about the best oil.
My $0.02 cents:
If you live in climates where the temperature varies from -40 to 100 winter to summer, it still might be a good idea to use synthetic in the run-off-the-mills' as well. Agree? Disagree?
the temps can range from 20F on the coldest winter nights to 115F
My $0.02 cents:
If you live in climates where the temperature varies from -40 to 100 winter to summer, it still might be a good idea to use synthetic in the run-off-the-mills' as well. Agree? Disagree?