Answer

Do the math for the make and model of your vehicle and the answer is “Yes, full synthetic oil is worth the additional cost” — if — it allows you to cut the # of oil changes per year in half. And still probably worth it, if you can cut the # of oil changes per year by a third.

For synthetic blend oils? You will be paying more annually, with no good research to suggest you will or won’t make that investment back later.

By reading this article, you will good, reference-based data to help you determine for your Toyota, Honda, Ford, Dodge, Audi or other car brand.

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OEM Oil Change Interval Recommendations

These are common oil change intervals for cars made after ~2016 To know the exact manufacturer’s for your make and model, it is recommended that you look in the owner’s handbook that came with your vehicle. European OEMs have recommended only full synthetic from about 2010. For most models the OEM recommends oil changes with conventional oil at 5,000 miles.

OEM
(2017-present)		 Conventional (miles) Blend (miles) Full Synthetic (miles) Notes (primarily for full synthetic oils)
Toyota 5,000 5,000 10,000 Only if using 0W-20 full synthetic and normal driving conditions
Honda 5,000-7,500 5,000-7,500 7,500–10,000 Based on Maintenance Minder system using synthetic 0W-20 or 0W-30
Ford 5,000-7,500 5,000-7,500 7,500–10,000 Assumes synthetic oil meeting WSS-M2C930-A spec; uses Intelligent Oil-Life Monitor
Chevrolet 5,000-7,500 5,000-7,500 7,500–10,000 Based on Oil Life Monitoring System; oil must meet dexos1 Gen 3
Nissan 5,000 5,000 5,000–7,500 Applies to synthetic 0W-20 under normal use; more often in severe conditions
Hyundai 5,000-7,500 5,000-7,500 7,500–10,000 Assumes synthetic oil meeting API SN+ or better; varies by engine type
Kia 5,000-7,500 5,000-7,500 7,500–10,000 Follows same guidance as Hyundai; 0W-20 or 5W-30 synthetic
Mercedes-Benz n/a n/a 10,000–15,000 Synthetic only; must meet MB 229.5 or 229.51 specification
BMW n/a n/a 10,000–15,000 Synthetic only; BMW Longlife-01 or 04 oil required
Volkswagen n/a n/a 10,000 Requires VW 502 00 or 508 00 rated full synthetic oil

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    What Is True

    1. Full synthetic oil has better durability and longer oil change intervals.

      • Some brands like Mobil 1 advertise 10,000–15,000 miles per change, and testing confirms lower breakdown rates.

      🔗 Mobil 1 Extended Performace

    2. High-mileage oils are a marketing category with minor, targeted benefits. .
      • They contain seal conditioners and extra detergents to reduce minor leaks and clean older engines.
      • These benefits are intended for engines over 75,000 miles.
        • The majority of high-mileage formulations—like Valvoline MaxLife, Pennzoil High Mileage, and Castrol GTX High Mileage—are labeled as synthetic blends, even if the front label emphasizes “high mileage” more than “synthetic.”
        • Full synthetic high-mileage options do exist (e.g., Mobil 1 High Mileage), but they are in the minority and priced higher.
    3. Full synthetic oils reduce engine friction and improve fuel efficiency—slightly.
      • AAA testing showed synthetic oil outperformed conventional by 47% in lab-based measures, including oxidation resistance, deposit prevention, and viscosity retention.
      • Fuel economy gains were ~2% in controlled conditions.
    4. There is no documented fuel efficiency or wear benefit from synthetic blends.
      • Synthetic blends are typically conventional oil with a small amount of synthetic to meet API (American Petroleum Institute) specs.
      • No independent lab or field data supports fuel efficiency or durability benefits.

  • What Is Not True

    1. That high-mileage oils prevent or delay major engine repairs.

      • There is no independent or OEM-backed research confirming a reduction in the likelihood of repairs like gasket replacements or rebuilds. 🔗 Cars.com

    2. That full synthetic oil dramatically increases engine life under normal use.

      • No long-term, large-scale field study compares engine lifespan of synthetic vs. conventional oil users in normal driving.

      • OEMs generally recommend full synthetic when engine design requires it, not for lifespan extension.

      • 🔗 Edmunds

    3. That synthetic blend is a meaningful upgrade for most drivers.

      • Most blends are created to meet minimum API standards at a lower price point—not for performance.

      • They offer no proven fuel savings and perform closer to conventional oil than to full synthetic.

      • 🔗 AutoZone

Do the Math

Full Synthetic (“synthetic” in the table) means fewer trips to the auto shop.

If you are willing to spend ~$8 more in exchange for cutting your trips to the service station in half, then full-synthetic is an easy choice. You save time and take advantage of all the verified benefits that come from a higher performing oil; even if the actual benefits or payback isn’t clear. These benefits are just upside, where the true benefit is time savings.

This is true for your old or new vehicles.

Financial Model

Year Oil Type Oil Cost ($) Fuel Savings ($) Repair Deferral ($) Annual Cost ($)
1 Conventional 150.0 0.0 0.000 150.000
1 Blend 240.0 0.0 0.000 240.000
1 Synthetic 200.0 42.0 0.000 158.000
10 Synthetic 200.0 42.0 966.913 -808.913

Financial Model Assumptions:

    • Annual Mileage: 15,000 miles
    • Oil Change Intervals: Conventional / Blend Oil: 5,000 miles and Synthetic Oil: 10,000 miles
  • Oil Type Fewer Oil Changes? Why/Why Not
    Conventional ❌ No Typically 3,000–5,000 miles. Breaks down faster.
    Synthetic Blend ❌ No Often still recommended at 5,000 miles by OEMs.
    Full Synthetic ✅ Yes (many cases) Can last 7,500–15,000 miles depending on brand and vehicle.
    • Cost per Oil Change Cists: Conventional Oil: $50 , Blend / High-Mileage Oil: $80 , Synthetic Oil: $100
    • Fuel Efficiency Improvement with Synthetic Oil: 2%🔗 Machinery Lubrication
    • Average Fuel Price: $3.50 per gallon 🔗 Financial Edge / Wall Street Prep
    • Average Fuel Economy: 25 miles per gallon
    • Major Engine Repair Cost: $1,500
      • Repair Deferral Benefit: Assumes synthetic oil delays major engine repair by one year. which means you will still have the engine repair in year 11.
    • Discount Rate: 5%

Preventing Major Engine Repair

It is generally believed that full synthetic oils can delay small and major repairs. Delaying them by just one year saves a lot of money in Year 10, but you have to pay for it in Year 11 anyway. However, this delay, depending on when you sell a car, can mean full savings, especially if the repair is delayed for years.

 

What Is Synthetic Oil?

Synthetic oils have superior additives in them that keep the oil in good condition over time. Typically, high performance vehicles require the use of synthetic oil.

Auto manufacturers are increasingly turning toward synthetic oils or synthetic blends (which are more affordable) because of the associated benefits.

High Mileage Vehicles

How Does Conventional Oil Compare?

Finding independent, non-industry-funded research that compares high-mileage synthetic oils to conventional oils in older vehicles is challenging. However, a study done by the American Automobile Association (AAA) in 2017 provides some insight:​

AAA’s Findings: The study revealed that, on average, synthetic oils outperformed conventional oils by 47% in various tests, including those assessing shear stability, deposit formation, volatility, cold-temperature pumpability, oxidation resistance, and oxidation-induced rheological changes. newsroom.aaa.com

The claims are… Synthetic oil takes care of your engine better than conventional oil, according to information released by AAA. There are a number of benefits associated with using synthetic oil. For example, if you live in an area where it gets either very hot or very cold, synthetic oil helps to protect your car’s engine more effectively because it does not break down as quickly. If you have an older car, synthetic oil can keep sludge from accumulating in the engine, which can have disastrous consequences for your car.

Do you drive short distances? Conventional oil may break down more quickly because it just doesn’t have time to get hot enough to do the job it was meant to do. Also, if you carry around heavy material in your vehicle, synthetic oil is the better choice. It takes longer to break down, which means that it is more efficient for the work you are doing.

In addition to the benefits stated above, synthetic oil is popular because it lasts for a very long time. Years ago, you had to change your oil every three thousand miles. That has changed a little bit now, with some brands of oil lasting several thousand miles more than that. Synthetic oil takes things to the extreme, however. At minimum, you do not need to change the oil until you hit 15,000 miles, and some people believe you can go up to 25,000 miles. It is important to have an understanding of what the manufacturer recommends and then stick to that; for example, if it is recommended that you change the oil every six months, you should follow that recommendation.

While you need to make the decision on your own as to whether synthetic oil is worth the cost or not, there are a lot of advantages to using it. Not only does synthetic oil last longer than conventional oil, but it is good for the environment as well. At Ethan’s Honest Automotive, we’re happy to take a look at your vehicle and make recommendations for you. We’ll also handle all your oil changes and any other maintenance that you need on your car. Come see us today!