Dear Car Talk:
I recently sold my 2009 Lexus ES350. It required premium unleaded gasoline (even noted on fuel cap), and I never had any problems with it.
In March 2019, I bought a 2019 Lexus ES350. I was told by the salesperson that I should use regular unleaded gasoline (also noted on fuel cap).
But the salesperson, and later a service adviser from Lexus, were not able to clearly explain why this new Lexus ES350 should use regular unleaded rather than premium unleaded gasoline.
I am hesitant to use regular unleaded gasoline. Do I continue to use premium unleaded gasoline, or do I save money by using the regular?
I enjoy reading your column every Saturday morning while I drink my cup of coffee. Thank you. -- Lucy
You save the money, Lucy. And with the money you save, you'll more than pay for every one of those Saturday morning cups of coffee, maybe even a few bran muffins.
In 2009, Lexus wanted more power from the ES350's six-cylinder engine. One way to get more power is to increase what we call the engine's "compression ratio." Basically, the compression ratio measures how much pressure is created in the cylinders when the air and fuel mix is compressed.
So, the 2009 Lexus had what's called a "high-compression engine." The problem with high-compression engines is that they can cause the fuel mixture to detonate too early -- before the spark fires -- just due to the high pressure. That's called pre-ignition, which causes knocking and pinging that are bad for the engine.
To combat that, the manufacturer requires you to buy a high-octane fuel. The primary characteristic of high-octane fuel (other than a high-octane price) is that it has a higher ignition point. That eliminates the pre-ignition problem.
But it costs you an extra 25 cents or so a gallon. And if you drive 15,000 miles a year, that's an extra $150 in fuel costs. Or $1,500 over 10 years.
You're lucky they figured out how to make an engine in 2019 that's not only more powerful and gets better fuel economy, but also runs on less expensive fuel.
That's called progress.
Your old Lexus made 272 hp and was rated at 23 mpg overall. The new one makes 302 hp and gets 26 mpg overall. Plus, it comes with a free cup of coffee every week to help you choke down our questionable car advice.