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Oil, Filters, Flushes

No guarantees are made on the results, and anything you do yourself is at your own risk.

Oil, Filters, Flushes
By Jesda Gulati 

I recommend, for a clean engine, using Mobil 1 0w-40 or 5w-40 (also known as the Truck/SUV formula) all year around. I experience harsh midwest winters and long humid summers, and drive hard. Mobil 1 10w-30 was a bit too thin on my Q45 in the summer and sometimes caused a clattering noise on startup if the car sat for a few days without being driven.

Mobil 1 is also the most accessible high-quality synthetic oil, available at any Wal-Mart, making it extremely handy for getting an oil change during a road trip. For $30-$35 at any Wal-Mart in the country, you can have your oil changed, fluids checked, and carpets vacuumed within minutes. Just be sure to provide Wal-Mart with your own filter, since they only carry Fram (not recommended). Wal-Mart's own brand of Supertech filters, made by Champion Labs, will suffice.

Mobil is now offering Mobil 1 Extended Performance, supposedly good for 15,000 miles. No matter what motor oil you use, we recommend AGAINST EXTENDED OIL CHANGE INTERVALS. This may be a marketing move by Mobil to compete with AMSOIL. Regular oil changes (2900-5000 miles) are important for keeping the filter new, the oil level sufficient, and contaminants and condensation out. For regular motor oil, the Q45 owners manual suggests a 3,750-mile oil and filter change interval.

Wal-Mart now offers its own brand of full synthetic motor oil called "Supertech", which has performed admirably in my Q, though I have no oil analysis data to prove its performance compared to Mobil 1. Supertech is bottled for Wal-Mart by Quaker State. See proof of Supertech being bottled by Quaker State.

AMSOIL, Valvoline Synpower, and Redline are also worthy alternatives to Mobil 1.


Wix, Napa Gold, Mobil 1, Bosch Premium, or Nissan oil filters are strongly recommended. Joe at Infiniti of Scottsdale offers low prices on Mobil 1 and Nissan filters. Buy a few and keep them handy. If you find yourself in a tight place and have no access to anything but the filter selection at Wal-Mart, the higher-end Fram (X2, Double Guard) products will suffice. Wal-Mart's low-cost Supertech filters are made by Champion Labs, and are considered superior to Fram's basic filters. There are horror stories about Fram's basic filters falling apart and destroying engines -- avoid them, please.

Before switching to a synthetic:

1. Run an oil with high levels of detergents, such as Valvoline Durablend, Valvoline Maxlife, or Mobil 1 5w40 Truck/SUV, to clean out sludge and deposits before switching. The reason for this is, most full synthetic oils such as standard Mobil 1 contain fewer detergents, as they are not as necessary with a cleaner running oil.

2. Most Nissan and Infiniti dealers offer a BG, Bilstein, or Envirolution motor flush for $80-$150, which runs a heated chemical through your motor and effectively cleans oil passages. The Gumout flush is NOT RECOMMENDED and could damage your engine if it is severely sludged.

Why synthetic?

This is a controversial subject, but synthetic oils tend to be cleaner, leaving less sludge and fewer contaminants behind. Most importantly, they handle extreme temperatures in ways conventional oil cannot. Corvettes, for example, require Mobil 1 strictly because it eliminates the need for an oil cooler. No, the operating temperature is not lower. The synthetic oil is simply better at handling high temperatures (resistance to foaming). In the winter, they have a lower pour point, allowing better lubrication during a cold weather start, which is when the most severe engine wear occurs. To a smaller degree, they reduce friction and slightly improve fuel economy, but don't expect your Q45 to magically achieve 30mpg.

What do you use?

The following motor oils and filters have performed admirably in my 1992 Q45.

6.5 quarts Supertech 5w-30 or 10w-30 ($17) or
Mobil 1 5w-40 full synthetic motor oil ($28)

1 regular Supertech oil filter ($2) or
1 Nissan oil filter or ($10) or
1 Bosch Premium oil filter ($6.50) or
1 Mobil 1 oil filter ($12)
Napa oil filters also appear to be well made.

Changed every 2900-3700 miles.
Why timely oil changes are as important as mileage intervals.

I take numerous short trips and have many starts throughout the day, along with wide open throttle runs -- considered a very severe duty cycle.


A thinner/lighter synthetic oil is suggested for winters where cold startups require easy flow for proper lubrication. We suggest a synthetic 0w-40/30 or 5w-40/30.

From regarding oil weights and cold weather:
The 5w number is completely and totally not comparable to the other number. the Xw number is derived from a cold cranking simulator test; the other number is the kinematic viscosity at 212 degrees F. ANY fluid for the most part thins as it gets hotter and thickens when it gets cold. Motor oil gets hundreds of times more viscous when it gets cold compared to when it's hot and at operating temperature. So, 5w-30 means that the oil passes the 5w cold cranking test (meaning it cranks less than 7,000 Cp at -30 degrees C) and it has an operating temperature viscosity in the 30 weight range (9.3Cst to like 12.3 Cst? or something like that)."

Run a synthetic in the winter.

Procedural notes:

Most Q45 owners prefer to have someone else change their oil, due to the filter location and removal process for the underbelly cover.
BE CERTAIN that when you leave the shop, your underside plastic cover is in place (assuming you had one when you went in).
Also BE CERTAIN that the oil filter is replaced from the bottom, NOT from the top, as that could damage the mass air flow sensor or MAF connector. receives NO funding or sponsorship from any outside sources.
Conclusions are based on personal judgement, data, and experience, not economic motives.

This web site is the copyrighted intellectual property of Jesda Gulati and Wes Stinson.