My Half Price Ride - Errata

The Elephant in the Room

Cars are extremely convenient and useful. That comes at a price. More affordable options exist, depending on your living situation:

• Walking
• Public transit
• Cycling
• E-Bikes

Online Car Buying

I’m not great at waiting. I kept my eyes open for other opportunities. I would see occasional listings for cars at good prices, from a company called Carvana. That caught my eye.

Then I did my homework. Hidden behind their ads and fancy website was the behavior of a shady dealership. They would sell cars they didn’t own. Many, many, many people had trouble getting their titles/registration after they had bought and paid for their car. Sometimes they would get their car repossessed despite having paid for it! A few were even put in jail for driving their car without valid registration.

I stopped looking at Carvana. If Carvana screwed up my car purchase, as they had with so many others, I’d need to hire a lawyer. Lawyers are expensive.

In 2025, research surfaced showing that Carvana’s business is a multi-billion dollar pump-and-dump scheme for their executives, “In the end, the Garcias (CEOs) will bank billions. For customers, they face the prospect of inferior or potentially dangerous cars due to cost cutting measures favoring the bottom line over quality and safety.”

Sometimes, the wise thing to do is walk away.

Total Cost of Ownership Calculations

These can be pretty complex. I made several operating assumptions in my calculations.

• If the vehicle lasts longer than 10 years, I will assume I’m going to sell it, and the $ from the sale is subtracted from its original purchase price.
• If the vehicle doesn’t last 10 years, I am assuming I will need to buy a vehicle when it dies, so its purchase price (minus its sale price at the 10-year mark) is added in. However, that next vehicle will likely last longer than the 10 year timeframe, so I only include a fraction of its purchase price.

Inflation

There’s been a lot said about inflation over the last few years, rightly so. One of my inspirations was a New York Times article describing how Argentinians live in times of high inflation. One of their key decisions? Make capital purchases soon, because the price of big-ticket items outpaces income. Big things become more expensive over time.

I’m making several assumptions about inflation:

• It will be elevated for at least 4 more years
• Inflation will affect car prices, car repair prices (parts+labor), and car insurance.
• The cost of fuel will also rise, though perhaps at a different rate from ‘overall’ inflation. It certainly won’t go down for very long.

Make and Model Filter

I’m aware that the criteria I used, especially the reliability score, eliminated a lot of potential options. That was worth it to me, because a car with a lower-but-still-decent reliability score would to run into more situations where it needed more expensive repairs.

Toyota Prius Prime Design

The 2018 Toyota Prius Prime I bought is complex in some ways, simple in others. It has some complicated components, like its HVAC or hybrid/battery systems.

It also is simpler than many cars: there is no starter, alternator, turbocharger, power steering pump/lines/fluid, or drive belt. The water pump and rack-and-pinion are electric, so they’re likely to last longer. The transmission has only gears & electric motors, no clutches or discs, and thus has a reputation for durability..

Finally, these cars have a reputation for long-term reliability. It’s a Toyota, a Prius, and more specifically, a 4th-generation Prius. They’re odd-looking but highly reliable. I’ll choose that combo in a heartbeat.

Here are the notes I took on how my Toyota Prius Prime is designed and built, and useful notes on its maintenance over time….

Oil Changes

• Use the engine oil viscosity that’s written on the car, usually the oil-fill cap. It’s 0W-20 for my car.
  • Toyota 0W-20 engine oil is made by Mobil1. OW-20 is synthetic already
• All gas engines drop some gas in the oil. This slowly dilutes it slowly, and it won’t work as well. Engines can put moisture in their oil if they don’t run up to temperature (i.e. lots of short trips).
  • Engines don’t like to be idle, they’ll develop internal issues.
  • A Prius Prime engine will run significantly less than usual, since the electric motors are moving the car a large fraction of the time.
  • So, get oil changes every 5-6K months anyways, even though the engine would have only ‘driven’ 2-3K miles. It’s cheap insurance. Go by time or mileage, whichever is sooner
• Hybrid engines start using one of the electric motors (MG1), not a starter. So, they starter at 800-1200 RPM rather than a ‘regular’ starter’s ~200RPM.
  • Don’t overfill hybrid engine when replacing the oil. With hybrids in particular, it will really affect it. The oil will get into the intake manifold.
  • This will lead to cold-start problems, misfires, everything gets clogged
  • Slightly underfill them if need be
• Never measure or correct the oil level when the engine is cold
  • To test it, run the car for 10 minutes to heat the oil up, let it cool for 5 minutes, then check the dipstick
  • The engine oil level will be a little lower when the engine is cold, the fluid will expand as it warms up, and raise the oil level.
  • Leave the oil level halfway between the 2 dots on the dipstick
• All about Costco (Kirkland Signature) engine oil
  • Cartalk, Bob the Oil Guy, r/prius, r/Costco, Project Farm, MotorAudit, Bob the Oil Guy 2
• Oil filters. Use the original Toyota filters. Get them in bulk?
  • Toyota filter is probably 90915-YZZF2
  • According to parts.toyota.com, it’s 90915-10009 based on the VIN number. The style changed partway through the 2018 Prius Prime model year, so I need to be careful on this one.
  • I will need 3-4 oil filters a year. So, get up to 8 at a time (2 years’ supply) if there are deals.

Filters (DIY)

• Engine air filter - replace it when it’s dirty. DIY. Use a Toyota one to maintain quality, they’re usually $10-20.
• In-cabin air filter. Replace it when it’s dirty. Use the activated charcoal one for better air filtration. However, the ‘activated’ part of the filter only lasts a year, so replace it at least annually. This doesn’t need to be a Toyota part, it just needs to be good quality.
• Hybrid fan filter
  • See the note above
  • Use compressed air to clean it out

Wipers & AC

• Wipers
  • Toyota OEM wipers (not Sightlines) are the best you’ll ever have
    • Dealership sells wiper inserts for these. You’ll probably only ever get them at a dealership, or online. Dealerships will often swap them for free.
  • Sightlines are the worst wipers ever made. Don’t ever buy it from the dealership, b/c it says Toyota on it
  • Go ahead and buy other reputable brands if the OEM ones are gone/broken.
• AC
  • “You need an A/C refresh service”, “It’s time to recharge your A/C” <- don’t fall for it.
    • Why are you recharging your A/C if it’s working perfectly? If it’s ice-cold and the A/C works great, you don’t need to do anything to it. It’s a sealed system, not susceptible to moisture without a leak.
  • If the A/C fluid is low, then it’s an issue. Might be a leak.
  • If there’s no leak, it’ll work forever
  • With a Prius Prime in particular, do not trust the HVAC system to anyone who’s not a Toyota/dealership mechanic trained on this system. The heat pump system is crazy complicated.
  • You need to clean your ducts, get rid of the mold. <- Only if it smells bad
    • Toyota comes with a duct cleaning kit, not too expensive. You can DIY, need to crawl under the car to find the drain, though.

Coolant and Transmission

• Engine Coolant. Gen4 Prius Primes use the ‘pink’ Toyota Super-Long-Life Coolant (SLLC).
  • All coolant becomes slowly more acidic over time, and acidic coolant will start to degrade hoses & seals. It’s far cheaper to replace the coolant than deal with that.
  • The first drain-and-replace is is after 5 years or 100K miles, whichever is sooner
  • After that it’s every 5 years or 50K miles, whichever is sooner.
  • How to replace engine + inverter coolant in hybrids
  • Looks like it needs 6 liters + 1.4 liters = 7.4 liters, or about 2 gallons’ worth
    • How to replace inverter & engine coolant DIY
• Hybrid System / ‘Inverter’ Coolant
  • This is used to cool the electronics in the inverter. Arguably it’s even more important to maintain this on a ‘Prime because the inverter is doing more work (more powerful batteries + motors = inverter doing more work)
  • The hybrid coolant circuit uses the same pink SLLC coolant as the engine.
  • Replace it on the same schedule as the engine coolant
  • First drain-and-replace is is after 5 years or 100K miles, whichever is sooner
  • After that it’s every 5 years or 50K miles, whichever is sooner.
  • How to replace engine + inverter coolant in hybrids
• Transmission Fluid
  • The transmission has no really ‘hydraulic’ parts, it’s 2 electric motors and a lot of gears. (LINKME JOHN WEBER VIDEO).
  • So, the transmission fluid is only used for lubrication and cooling in Prius transmissions, not as a hydraulic fluid.
  • So, its replacement intervals don’t have the same ‘sweet spot’ calculations as a normal transmission. They can be changed at any time. 60-90K is a good sweet spot range.
  • DIY how to replace transmission fluid in hybrids
  • Go with OEM fluid. Uses Toyota ATF WS fluid. Needs 3.9 quarts, get 5 just to be safe.
    • Get 2 replacement transmission plug gaskets as well, for the drain + fill plugs. They’re metal.
    • Get the ATF WS fluid wherever you can find it at a discount. Some dealerships will run occasional specials.
    • Don’t take the gamble with aftermarket fluid. The transmission is expensive in a Prius, due to the electric motors inside. Don’t risk it.
• Coolant Pumps
  • The main engine coolant pump is electric. So, there’s no worry about a drive belt or belt pully wearing out.
    • Because it’s electric, it can’t use normal lubrication oil, it has to be non-conductive.
    • Question - does it run off the 12V circuits in the car? Or is it using a higher voltage, perhaps directly from the inverter?
  • There’s also a separate, smaller pump that’s used for moving the hybrid system coolant, sometimes called the ‘inverter pump’ or ‘inverter coolant pump’. It’s electric as well.

Brakes and Spark Plugs

• Brakes
  • There are dealership ones, and a lot of good aftermarket options.
    • Do research or else get the dealership ones.
  • At a dealership, you need to replace the pads and the rotors. Prius rotors aren’t big/thick enough to resurface.
    • There are 2 kinds of brake pads. There’s the original ones, they come from the factory, they’re semi-metallic
    • They also sell identical pads, but they’re called ‘economy’ or ‘value’ or ‘ceramic’ pads. They’re made to compete with aftermarket, so they’re going to be cheaper. Go for these
      • They will have ‘AZ’ in the part number
  • Newer Toyotas, you often need to replace the rotors. It’s expensive.
    • You can get aftermarket rotors as well, if it’s a good option and significantly cheaper
  • Original parts come with warranty
  • Don’t throw out the original pads, because they have a shim kit. Aftermarket/cheaper pads have the shim kit glued on. Transfer the shim kit to the new pad. Remove the glued-on ones and put the shim kit back on it with some good grease. Save them, at the least
  • Always ask for your old parts. Walk away from any mechanic that doesn’t give you parts back
  • The parking break for a Gen4 Prius is a wire-type. When you put on the emergency brake, it pulls a wire/cable to the back wheels, which forces the brake caliper there closed. It’s not electronic.
• Brake Fluid
  • “You need a brake fluid, brake flush, it looks dark, etc” at a mechanic. Walk away / ignore them. The way to check brake fluid is by moisture content or copper content. Ask to see the results.
  • It absorbs moisture over time. The color doesn’t tell you much, some are dark to begin with (dot4 and higher grades)
  • Average, every 3 years or so. Toyota doesn’t specify when to replace it. They say when to inspect it
  • Buy the same aftermarket fluid, you don’t need the original stuff.
  • DOT3 tends to last a little longer. DOT4 has a higher boiling point (it doesn’t boil until a higher temperature), making it more suitable for long/intense braking.
• Spark plugs
  • Newer cars, including all Primes, use iridium plugs. They’re good for 10 years or 120K, whichever is first.
    • If it’s in a well-maintained car, the spark plugs won’t go bad at all
  • Get OEM/dealership plugs, or else buy online for the same part number. You can get close to OEM by buying Denso if you want to save a few bucks, but make sure the source is reputable.

Injectors, Battery, Tires, Drive Belts

• EGR
  • A common problem with Gen3 Priuses. The valve will get stuck open, and cause a rough ride.
  • EGR Diagnosis & Repair Tips
  • Gen4 EGR
  • A less common issue for Gen4, but it’s not clear how much less common.
  • To research - how often to clean out the EGR system in a Gen4 Prius, and why.
• Fuel Injection
  • ‘Fuel injection service’, ‘fuel cleaning service’, ‘induction cleaning’
    • If the injectors weren’t clean, you’ll notice. Fuel economy crashes, the car won’t run correctly
  • EFI tank additive…is garbage. Doesn’t do anything. Skip it.
  • Go for Top Tier fuel instead, the additives keep the car clean.
  • Fuel Injector cleaner does something else…it de-carbonizes the engine, the valves & pistons
  • If you take cold trips, never really go on the freeway, you never give the engine the chance to ‘blow everything out’ and clean it up
  • Instead, take the car on the highway, go on the highway and floor it, blow everything off
  • Throttle bodies do get gunk buildup. Clean them every 30-60K miles. Maybe even up to 100K miles. If not DIY, ask specifically for this to be cleaned.
• 12V (small) Battery
  • Most Toyotas have a great battery. Shop around for batteries. Look for the best battery warranty you can find.
  • Toyota battery is made by Interstate
  • Basic battery has an 84-month battery, but it’s prorated after 2 years
  • Batteries become unpredictable between 3-5 years
  • Common wisdom on Prius group chats/forums is that the 12V batteries only last 5-6 years, max.
• Large (‘Traction’) Battery
  • The top 5-10% and the bottom 15-20% of the battery is ‘inaccessible’ (not part of the 0-100% range for a Prius Prime), to make the battery last longer.
  • There are very, very few comments/cases of the ‘Prime battery dying. Some very old ones (200K+ miles) start losing range (say, 16-17 miles intead of 25), but the car still runs just fine.
• Tires
  • Most dealerships are very overpriced for tires. Discount Tire, Costco, Sam’s Club…look at those tires.
  • Stick with good brand names, don’t go for tires you’ve never heard of
  • Most cars have OEM tires, tirerack.com has them for sale
    • Always read reviews for the car you have
  • My personal note: Michelin tires are the ones that haven’t been affected by recalls/warranties/scandals, like Firestone or Bridgestone or Continental. I interpret as a signal that they are built to a higher standard.

Steering and Suspension

• Steering
  • The Gen4 Prius has ‘electric’ power steering (meaning no power steering pump, fluid, or lines). It’s more expensive initially, but they don’t run the risk of fluid leaks, which is usually what causes steering systems to go out.

Published 01 November 2024