TETROSYL - Engine Oil Additive

We offer a range of fast and convenient UK & European Home Delivery services.

Need it even quicker? Click & Collect for FREE in just 30 minutes from one of our 200+ stores nationwide.

UK Mainland

We offer free standard home delivery when you spend £25 or more, £3.95 for orders under £25*.

Need it even quicker? We have express shipping options available or you can use our free Click & Collect service, you can collect in just 30minutes from one of our 200+ stores.

The delivery information below applies to all orders placed by 8pm Monday - Friday only, not including Bank Holidays*.

^*Free delivery is applicable on all orders over £25 inc VAT to UK mainland addresses. This excludes Highlands, Isles, Northern Ireland or any offshore address, and oversized / overweight items.

^**These prices are applicable to UK mainland addresses only. Shipping charges for Highlands, Isles, Northern Ireland or any offshore address, and oversized / overweight items, will be subject to additional surcharges and will be advised at checkout. Some services may not be available to some locations.

Oversized and Overweight items: If your item is oversized (Over 1.5m) and/or overweight (Over 25kg), you may incur an additional charge. The cost will be automatically calculated at checkout.

Car Batteries & Bulky Items: Car batteries will be sent via a specialist courier, if your order contains other items they will be dispatched on your chosen service. Car batteries on premium services may incur an additional charge, this will be automatically calculated at checkout. Batteries are supplied in specialist packaging with the relevant health and safety precautions in place. Please ensure the box is not damaged in any way upon delivery, any returns will need to be sent back in the original packaging. If this isn't available, we are able to supply a replacement box for a small fee, please contact us to arrange this. Items over 1.5m and/or 20kg may incur an additional charge, this will automatically be calculated at checkout.

Delivery Estimations

We aim to dispatch all orders within one working day where products are shown as in stock. In most cases, for in stock items, we will dispatch all orders placed before 8pm the very same day. Orders placed after 4pm, over a weekend or bank holiday will be processed and dispatched on the following working day. Working days are Monday to Friday and exclude bank holidays.All deliveries will be made weekdays only; no deliveries will be made on weekends or Bank Holidays unless otherwise stated at the point of order.Delivery times for products that are being sent direct from the manufacturer will vary, please contact us to check. In cases where your order contains items being sent from the manufacturer and in-stock items, we will dispatch the in-stock items on the chosen service and the remaining goods will follow.

Please Note: The cut-off time for next day delivery is 8pm!

General Delivery Terms

We'll do everything we can to meet the delivery times above, however, they may be affected by factors outside of our control and can't be guaranteed. We'll endeavour to let you know if we become aware of an unexpected delay.

Please see our full Terms & Conditions for more information.

Highlands, Isles & Northern Ireland

Delivery Estimations

All orders for Highlands, Isles & Northern Ireland are shipped using a premium service. Delivery is typically between 2-4 working days, some exceptions will occur on oversized / overweight items. Deliveries will be made on weekdays only; no deliveries will be made at weekends or on Bank/Public Holidays.

Oversized and Overweight items: If your item is oversized (Over 1.5m) and/or overweight (Over 25kg), you may incur an additional charge. The cost will be automatically calculated at checkout.

Car Batteries: Batteries will incur an additional charge due to the requirement of specialist carriers. The cost will be automatically calculated at checkout. Batteries are not available for shipping to Northern Ireland, Isle of Man, or Isles of Scilly.

Dispatch Time

We aim to dispatch all orders within two working days from receiving your order where products are shown as in stock. In most cases, for in stock items, we will dispatch all orders placed before 8pm the very same day. Orders placed over a weekend or bank holiday will be processed and dispatched on the following working day. Working days are Monday to Friday and exclude bank holidays.

Delivery Estimations

Estimated delivery times are detailed above; some exceptions will occur on oversized / overweight items. Deliveries will be made on weekdays only; no deliveries will be made at weekends or on Bank/Public Holidays.

Oversized and Overweight items: If your item is oversized (Over 1.5m) and/or overweight (Over 25kg), you may incur an additional charge. We will contact you once your order is placed in these cases.

Car Batteries: Shipping is not available for batteries to Europe.

Oversized Items

Some parts are oversized and require specialist delivery service. We offer a premium delivery service for these parts, unfortunately there is no free delivery available. Items will usually take 2-4 working days to be delivered. The cost will be automatically calculated at checkout.

Overweight Items

Orders that are overweight (Over 25kg) may incur an additional charge. The cost will be automatically calculated at checkout.

Restricted Items

• Aerosols: We are unable to ship aerosols due to courier restrictions.

• Batteries: Can only be shipped to UK Mainland addresses only.

• Liquids: Can only be shipped to UK Mainland addresses only.

Specialist Items

Some products have restrictions or special conditions to enable shipping

• Car Batteries: Batteries are shipped in specially designed fit for purpose packaging. Please open the box carefully as any returns need to be sent back in the original box. If the box is not available, the battery must be returned in an equivalent box.

• Exhausts: Some exhausts are not available for home delivery, however, are available for Click & Collect.

• 20L Liquids: Single units of 20L+ liquids are not available for home delivery, however, are available for Click & Collect.

With over 200 store locations across the UK & Ireland, GSF Car Parts Click & Collect is the fastest and most convenient way of ordering car parts.

All our stores carry stock of the most popular and fast-moving parts, ready for you to collect in just 30 minutes.

Your local GSF store will receive, check, and pick your Click & Collect order ready for your arrival. Should there be any issues with the items ordered the local store team will get in touch.

Click & Collect orders are usually ready to collect in 30 minutes. If your order is placed outside of normal store opening hours, then it will be ready to collect 30 minutes after the store next opens for business.

Please note that the products will be only reserved until the end of the next working day, after which we cannot guarantee availability.

On arrival at your local GSF Car Parts store simply show your email confirmation or online order number to a member of staff at the collection counter. Any additional items you need can be added to your order before payment is taken in-store.

Need help or advice? Our friendly parts advisors have a wealth of knowledge and expertise so feel free to ask them any questions.

Should you need to return an itemfor any reason, simply bring it back to the local store from which you collected it. Please bring along your order invoice so we can process your return quickly.

In the very unlikely event that you have a problem with any product you have purchased from us, then please contact our Customer Support Team, who are ready to help and guide you through the faulty item warranty return process.

All the products we sell have a minimum of 12 months warranty (unless otherwise stated), which covers parts which are found faulty through manufacturing defects only. The warranty does not cover and we will have no liability to you in respect of any defect arising from wear and tear, willful damage, negligence, tampering of goods, abnormal working conditions, incorrect fitting or ordering of goods or failure to follow the manufacturer’s instructions.

You will complete a warranty claim form and return it back to us, upon return we will assess your claim, and if necessary, will collect the parts at our cost (UK mainland only). Where necessary to do so, goods will be sent for inspection and testing by the manufacturer, as per manufacturer conditions. The manufacturers' report will be final and we shall have no further liability to you. You will allow a reasonable opportunity for claims to be investigated by us/the manufacturer prior to any replacement, refund or credit being issued and where required provide additional information and or goods for inspection if requested by us or the manufacturer.

Any item which is proved and admitted by the manufacturer to be defective during the relevant warranty period due to material or structural defect will be replaced free of charge or refunded in full at our discretion. Under no circumstances will we accept liability for consequential loss or damage or pay for any repairs or alterations without prior authorisation.

We will have no liability with regard to any claim in respect of which you have not complied with the claims procedures in the Warranty Conditions.

All warranties provided are non-transferable and apply only for the original customer. The warranty starts from the date of delivery, if we replace the goods within the warranty period, the warranty does not start again, you will only benefit from the remaining warranty period. If you are exercising your ‘right to reject’, you must notify us prior to fitment of the goods and within the 30 day period. Once fitted we reserve the right to investigate your claim.

Under no circumstances will we accept liability to you in respect of costs incurred such as: (but not limited to) loss of earnings, travel expenses, recovery costs, damages etc.

Price Match Guarantee.

At GSF Car Parts, we want you to shop with complete confidence. We would never knowingly overprice our products and regularly review our pricing to ensure we remain competitive against other UK retailers. Although we work hard to maintain fair, low pricing, we understand there may be times when you find an item cheaper elsewhere. That’s why we offer a Price Match on the following brands: Drivetec, Delphi, Comma, FRAM, Magma, Katana, Hella, Rymec and Power Plus. If you find the same item from one of these brands cheaper from an eligible UK retailer within 7 days of your purchase, we’ll refund the difference.

How It Works

To qualify, the product must be identical to the one purchased (same brand, model/part number, full specification, and sold as new with a UK manufacturer warranty). The competitor must be a UK‑VAT Registered Retailer, with the item in stock and able to ship immediately to your postcode.

We compare the competitor’s lowest publicly available price, including VAT and the cheapest available delivery option. Any codes or offers must be visible on the competitor’s website. We cannot accept:

• Sign‑up or new customer discount codes

• Exclusive promotional/voucher codes sent via email or SMS

• App‑only, loyalty, membership or personalised pricing

Marketplaces (eg. eBay, Amazon, AutoDoc), second‑hand items are not included in the price match.

How to Claim

Contact our customer service team via email, telephone or live chat and include:

• Email:

• Telephone:

• Order Number:

• Link to the cheaper retailer:

Our team will review your request within 3 working days, and once verified, we’ll refund the difference to your original payment method.

What’s Excluded

• Clearance or distressed stock items

• Membership only or ‑trade only‑ pricing

• Flash sales lasting under 24 hours

• Non-U‑K retailers or overseas fulfilment

• Bundles where product contents differ

• Discounts applied onto bundles or sets

• Voucher codes, multibuy deals, loyalty/points‑based promotions

• Gift card offers, student/staff/Blue Light discounts

• Subscription or finance‑only pricing

• Corporate or volume quotes

• Prices requiring sign‑up, login, SMS/email exclusive codes

Returns Policy

As much as we would like you to be happy with your purchase, we know sometimes you may need to return items that you no longer need or aren't quite right for your vehicle. In any case, we are more than happy to offer a refund, up to 60 days from the date the parts were successfully delivered (As long as all goods are in original condition, in original packaging, are unused and unfitted, and are deemed as in a resaleable condition). All goods will be inspected before a credit is issued.

In-Store Purchases

Simply return the goods to your local store with your invoice or your order confirmation email within 60 days of purchase.
The store will inspect the goods before issuing a credit.

Home Delivery Orders

You can return Home Delivery orders to your local GSF store for free. The goods will be returned to our central distribution centre for inspection. All refunds are issued back to the original payment method, no refunds will be given in store.If you wish to return your item by post, you are responsible for all postage costs, appropriate insurance, and packaging, unless agreed in advance with our customer service team. If the goods are faulty, please continue to the section below. GSF Car Parts will not accept responsibility for loss or damage of goods during transit back to us. Please ensure you include a completed returns form with your parcel, failure to do so may result in a delay in processing your refund. A copy of the form can be downloaded on the link below.

Return Address

Ecommerce Returns
GSF Car Parts
Gravelly Way
Four Ashes
Wolverhampton
WV10 7FH

Faulty or Damaged Goods

If your item is faulty or damaged on arrival, please contact our customer service department.
Damaged goods will be replaced or refunded once we’ve reviewed the damage, please do not dispose of any goods until instructed by us. Where possible, please include photos of the damage in your initial contact with us.If your item is faulty, or goes faulty within its warranty period, we will provide you with a warranty claim form and arrange a collection of the goods. Please see our Terms & Conditions for more information