How Does Synthetic Motor Oil Increase Fuel Economy?

Increasing fuel economy remains a top priority for most automakers, and use of synthetic oil is just one of the many tools in their arsenals to build vehicles that deliver the power we crave without sucking too much gas.

So, how does synthetic oil increase fuel economy compared to conventional lubricants? Let’s find out.

For a deeper dive, read Synthetic vs. Conventional Oil: The Definitive Guide

Reducing viscosity increases fuel economy

At one time, most passenger cars/light trucks used 10W-40 motor oil. Then it was 5W-30. Today, many vehicles call for 5W-20, 0W-20 and even 0W-16 oil.

The lower the oil’s viscosity – defined as its resistance to flow – the more readily it flows.

Imagine a jar of honey and a glass of water. Stirring water with a spoon requires less energy than stirring honey. The same principle applies to your engine and motor oil.

Lower-viscosity oils are easier to pump through the engine and offer reduced resistance to moving engine parts, increasing fuel economy.

Why do synthetics offer an advantage in reducing motor oil viscosity?

Formulating a 0W-XX motor oil using only conventional base oils is extremely difficult, if not impossible.

Formulators can achieve the 0W rating, but the oil will vaporize more readily at higher temperatures. It’ll also fail other required industry tests.

Simply put, formulating lubricants is a give/take, and conventional base oils don’t provide near the performance as synthetics. This requires formulators to give up too much required performance in one area to gain it in another.

Synthetics offer better cold-flow ability

Synthetics’ improved flow during cold starts also improves fuel economy.

Since they don’t contain waxes, which are inherent to conventional oils, they don’t thicken as much when your vehicle sits overnight. In the morning, when you start your vehicle and drive away, the motor oil, transmission fluid and gear lube don’t require as much effort to circulate.

This results in less wasted energy and improved fuel economy.

It’s important to note that “cold” doesn’t only apply to us northern folks. “Normal” operating temperature for a vehicle can be up to 235ºF (113ºC). Anything below that is considered “cold” to your engine.

So, even down south at the height of summer, synthetics’ improved cold-flow can still help improve fuel economy.

Why pay more for gas? Switch to synthetics to maximize your mpg.


  1. I want to change my oil in my 2003 FORD F 150 to Synthetic oil. Do i need to do anything other than drain the old oil out and put the new in ?? it’s got the 5.4 liter and if it can help with performance I want Synthetic cause the miles are getting up there.

    1. Hi Robert,

      No, you don’t have to do anything special prior to switching to synthetic motor oil. Just drain the oil, replace the filter and refill. You can use an engine flush to remove accumulated deposits if you want. Check out this article we wrote on this topic.


  2. Hello Jim,

    John made some good points …

    Over in the European line of oils,

    Amsoil’s Mid SAPS 5.40 — AFLQT

    Meets the VW 501.00 and 505.01
    BMW Longlife-04
    Mercedes Benz 229.52
    Porsche A40

    And GM’s Dexos 2 higher performance standards.

    In my opinion, any oil capable of being used in gas or diesel powerplants
    With turbo or without –
    Must be one stout engine lubricant.

    I use it in all my customers’ Turbo Diesel and Turbo Gas engines.
    Selling the oil change by the first fill and doing a case and 2 filters
    for after the fact – when maybe they can not get back to me – when we
    are on different schedules or something.

    So, I’m just saying … AFLQT –
    is a great all season engine oil for many engines.
    Unless folks are traveling like a salesman –
    2 oil changes a year with this 5.40 ought to give you
    great protection and an increase in fuel economy as well.

    Take care,

    1. Hi Jim,

      Full synthetic motor oils don’t contain the conventional base oils found in synthetic-blend products, meaning they typically provide improved wear protection, engine cleanliness and fuel economy, among other benefits. In addition, there’s no definition for a “blend” – it could contain anywhere from a drop to mostly synthetic base oils, so it’s tough to predict performance.

      Also, the GM dexos1 specification doesn’t stipulate the motor oil you use must be a synthetic-blend. In fact, plenty of high-quality full synthetic motor oils available carry the dexos1 spec, including AMSOIL Signature Series, AMSOIL XL and AMSOIL OE Synthetic Motor Oils. Be sure to use the correct viscosity for your XTS.

Leave a Reply